Preparation of lactic acid bacteria compound starter cultures based on pasting properties and its improvement of glutinous rice flour and dough

The effects of 5 lactic acid bacteria(LAB)fermentation on the pasting properties of glutinous rice flour were compared,and suitable fermentation strains were selected based on the changes of viscosity,setback value,and breakdown value to prepare LAB compound starter cultures.The results revealed that Latilactobacillus sakei HSD004 and Lacticaseibacillus rhamnosus HSD005 had apparent advantages in increasing the viscosity and reducing the setback and breakdown values of glutinous rice flour.In particular,the compound starter created using the two abovementioned LAB in the ratio of 3:1 had better performance than that using a single LAB in improving the pasting properties and increasing the water and oil absorption capacity of glutinous rice flour.Moreover,the gelatinization enthalpy of the fermented samples increased significantly.For frozen glutinous rice dough stored for 28 days,the viscoelasticity of frozen dough prepared by compound starter was better than that of control dough,and the freezable water content was lower than that of control dough.These results indicate that compound LAB fermentation is a promising technology in the glutinous rice-based food processing industry,which has significance for its application.

Allergen degradation of bee pollen by lactic acid bacteria fermentation and its alleviatory effects on allergic reactions in BALB/c mice

Food allergy as a global health problem threatens food industry.Bee pollen(BP)is a typical food with allergenic potentials,although it performs various nutritional/pharmacological functions to humans.In this study,lactic acid bacteria(LAB)were used to ferment Brassica napus BP for alleviating its allergenicity.Four novel allergens(glutaredoxin,oleosin-B2,catalase and lipase)were identified with significant decreases in LAB-fermented BP(FBP)than natural BP by proteomics.Meanwhile,metabolomics analysis showed significant increases of 28 characteristic oligopeptides and amino acids in FBP versus BP,indicating the degradation of LAB on allergens.Moreover,FBP showed alleviatory effects in BALB/c mice,which relieved pathological symptoms and lowered production of allergic mediators.Microbial high-throughput sequencing analysis showed that FBP could regulate gut microbiota and metabolism to strengthen immunity,which were closely correlated with the alleviation of allergic reactivity.These findings could contribute to the development and utilization of hypoallergenic BP products.

Screening of glucosinolates degrading lactic acid bacteria and their utilization in rapeseed meal fermentation

Rapeseed meal is a promising food ingredient, but its utilization is limited by the presence of some potentially harmful ingredients, such as glucosinolates. Fermentation is a cost-effective method of detoxication but a food-grade starter culture with glucosinolates degradation capacity is required. In this study, 46 strains of lactic acid bacteria from traditional paocai brines were screened for their ability to glucosinolate degradation. The results showed that more than 50% of the strains significantly degraded glucosinolates. Two strains of Lactiplantibacillus(p7 and s7) with high capacity of glucosinolates degradation through producing enzymes were identified. Then,an optimized condition for rapeseed meal fermentation by p7 was established to degrade glucosinolates, which can achieve about 80% degradation. UPLC/Q-TOF-MS analysis showed that the degradation rate of individual glucosinolates was different and the degradation rate of gluconapin and progoitrin in rapeseed meal can reach more than 90%. Meanwhile, fermentation with p7 can improve safety of rapeseed meal by inhibiting the growth of Enterobacteriaceae and improve its nutritional properties by degrading phytic acid. The in vitro digestion experiments showed that the content of glucosinolates in rapeseed meal decreased significantly during gastric digestion. Meanwhile, fermentation with p7 can greatly improve the release of soluble protein and increase the contents of free essential amino acids, such as lysine(increased by 12 folds) and methionine(increased by 10 folds).

3D printed lactic acid bacteria hydrogel:cell release kinetics and stability

In this study,a new type of 3 D printed living biological hydrogel was developed by integrating lactic acid bacteria(LAB)into biocompatible and non-toxic polymer materials.Interestingly,the living materials loaded with LAB can be freeze-dried and reused for more than 100 times.The bio-hydrogel can be used to co-culture different LAB and keep its fermentation performance stable in long-term use.The release kinetics model and response surface method were used to simulate and optimize the bacteria release mode in the bio-hydrogel.The results show that the release of bacteria from hydrogel is regulated by the coupling of Fickian diffusion and polymer swelling.The stability of LAB hydrogel was evaluated by reuse experiments.The images of confocal microscopy and scanning electron microscope showed that the bacteria with high cell viability were distributed in the hydrogel and intact structure of the living hydrogel was maintained after 100 times of reuse as yoghurt starter.In conclusion,the 3 D printed LAB bio-hydrogel developed in this study has the advantage of reuse and sustainability,which is expected to open up a new way for the preparation of food culture starter.

Influence of lactic acid bacteria, cellulase, cellulase-producing Bacillus pumilus and their combinations on alfalfa silage quality

This study assessed the effects of lactic acid bacteria(LAB), cellulase, cellulase-producing Bacillus pumilus and their combinations on the fermentation characteristics, chemical composition, bacterial community and in vitro digestibility of alfalfa silage. A completely randomized design involving a 8(silage additives)×3 or 2(silage days) factorial arrangement of treatments was adopted in the present study. The 8 silage additive treatments were: untreated alfalfa(control); two commercial additives(GFJ and Chikuso-1); an originally selected LAB(Lactobacillus plantarum a214) isolated from alfalfa silage; a cellulase-producing Bacillus(CB) isolated from fresh alfalfa; cellulase(C); and the combined additives(a214+C and a214+CB). Silage fermentation characteristics, chemical composition and microorganism populations were analysed after 30, 60 and 65 days(60 days followed by exposure to air for five additional days). In vitro digestibility was analysed for 30 and 60 days. Compared with the other treatments, selected LAB a214, a214 combined with either C or CB, and Chikuso-1 had the decreased(P<0.001) pH and increased(P<0.001) lactic acid concentrations during the ensiling process, and there were no differences(P>0.05) among them. Fiber degradation was not significant(P≥0.054) in any C or CB treatments. The a214 treatment showed the highest(P=0.009) in vitro digestibility of dry matter(595.0 g kg–1DM) after ensiling and the highest abundance of Lactobacillus(69.42 and 79.81%, respectively) on days 60 and 65, compared to all of other treatments. Overall, the silage quality of alfalfa was improved with the addition of a214, which indicates its potential as an alfalfa silage inoculant.

Effect of lactic acid bacteria and propionic acid on conservation characteristics,aerobic stability and in vitro gas production kinetics and digestibility of whole-crop corn based total mixed ration silage

This study was conducted to evaluate the effect of lactic acid bacteria and propionic acid on the fermentation quality, aer- obic stability and in vitro gas production kinetics and digestibility of whole-crop corn based totalmixed ration （TMR） silage. Total mixed ration was ensiled with four treatments： （1） no additives （control）; （2） an inoculant （Lactobacillus plantarum） （L）; （3） propionicacid （P）; （4） propionic acid＋lactic acid bacteria （PL）. All treatments were ensiled in laboratory-scale silos for 45 days, and then subjected to an aerobic stability test for12 days. Further, four TMR silages were incubated in vitro with buffered rumen fluid to study in vitro gas production kinetics and digestibility. The results indicated that all TMR silages had good fermentation characteristics with low pH （〈3.80） and ammonia nitrogen （NH3-N） contents, and high lactic acid contents as well as Flieg points. Addition of L further improved TMR silage quality with more lactic acid production. Addition of P and PL decreased lactic acid and NH3-N contents of TMR silage compared to the control （P〈0.05）. After 12 days aerobic exposure, P and PL silages remained stable, but L and the control silages deteriorated as indicated by a reduction in lactic acid and an increase in pH, and numbers of yeast. Compared to the control, addition of L had no effects on TMR silage in terms of 72 h cumulative gas production, in vitro dry matter digestibility, metabolizable energy, net energy for lactation and short chain fatty acids, whereas addition of PL significantly （P〈0.05） increased them. L silage had higher （P〈0.05） in vitro neutral detergent fiber digestibility than the control silage. The results of our study suggested that TMR silage prepared with whole-crop corn can be well preserved with or without additives. Furthermore, the findings of this study suggested that propionic acid is compatible with lactic acid bacteria inoculants, and when used together, although they reduced lactic acid production of TMR silage, they improved aerobic stability and in vitro nutrients digestibility of TMR silage.

The effects of fermentation and adsorption using lactic acid bacteria culture broth on the feed quality of rice straw

To improve the nutritional value and the palatability of air-dried rice straw, culture broth of the lactic acid bacteria community SFC-2 was used to examine the effects of two different treatments, fermentation and adsorption. Air-dried and chopped rice straw was treated with either fermentation for 30 d after adding 1.5 L nutrient solution（50 m L inocula L–1, 1.2×1012 CFU m L–1 inocula） kg–1 straw dry matter, or spraying a large amount of culture broth（1.5 L kg–1 straw dry matter, 1.5×1011 CFU m L–1 culture broth） on the straw and allowing it to adsorb for 30 min. The feed quality and aerobic stability of the resulting forage were examined. Both treatments improved the feed quality of rice straw, and adsorption was better than fermentation for preserving nutrients and improving digestibility, as evidenced by higher dry matter（DM） and crude protein（CP） concentrations, lower neutral detergent fiber（NDF）, acid detergent fiber（ADF） and NH3-N concentrations, as well as higher lactic acid production and in vitro digestibility of DM（IVDMD）. The aerobic stability of the adsorbed straw and the fermented straw was 392 and 480 h, respectively. After being exposed to air, chemical components and microbial community of the fermented straw were more stable than the adsorbed straw.

The effect of lactic acid bacteria inoculums on in vitro rumen fermentation, methane production, ruminal cellulolytic bacteria populations and cellulase activities of corn stover silage

The objective of this study was to investigate the effect of lactic acid bacteria(LAB) inoculums on fermentation quality and in vitro digestibility of corn stover silage.Corn stover was ensiled without(control) or with Lactobacillus plantarum(LP),Enterococcus faecalis(EF),and Enterococcus mundtii(EM) for 45 days.The fermentation characteristics were assessed,and subsequent in vitro dry matter digestibility(DM-D),neutral detergent fiber digestibility(NDF-D),volatile fatty acids(VFA),methane(CH4) production,cellulolytic bacteria proportions and their activities per corn stover silage were also determined.There was no significant difference(P>0.05) among the silage pH,lactic acid,crude protein(CP),water soluble carbohydrates(WSC) and lignocelluloses contents of different treatments.The relative proportions of Ruminococcus flavefaciens and Fibrobacter succinogenes,carboxymethyl-ocellulose and β-glycosidase activities,DM-D,NDF-D,and VFA production of in vitro incubation was higher(P<0.05) for silages inoculated with LP and EF than those of the control silage.Silage inoculated with LP showed the lowest(P<0.05) CH4 production per unit yield of VFA,which was positively corresponded to the lowest(P<0.05) ratio of acetate to propionate.In summary,the ensiling fermentation quality and subsequent utilization of corn stover silage were efficiently improved by inoculated with L.plantarum.

Application of Lactic Acid Bacteria(LAB) in Freshness Keeping of Tilapia Fillets as Sashimi

Aquatic products are extremely perishable food commodities. Developing methods to keep the freshness of fish represents a major task of the fishery processing industry. Application of Lactic Acid Bacteria(LAB) as food preservative is a novel approach. In the present study, the possibility of using lactic acid bacteria in freshness keeping of tilapia fillets as sashimi was examined. Fish fillets were dipped in Lactobacillus plantarum 1.19(obtained from China General Microbiological Culture Collection Center) suspension as LAB-treated group. Changes in K-value, APC, sensory properties and microbial flora were analyzed. Results showed that LAB treatment slowed the increase of K-value and APC in the earlier storage, and caused a smooth decrease in sensory score. Gram-negative bacteria dominated during refrigerated storage, with Pseudomonas and Aeromonas being relatively abundant. Lactobacillus plantarum 1.19 had no obvious inhibitory effect against these Gram-negatives. However, Lactobacillus plantarum 1.19 changed the composition of Gram-positive bacteria. No Micrococcus were detected and the proportion of Staphylococcus decreased in the spoiled LAB-treated samples. The period that tilapia fillets could be used as sashimi material extended from 24 h to 48 h after LAB treatment. The potential of using LAB in sashimi processing was confirmed.

Potential applications of lactic acid bacteria and bacteriocins in antimycobacterial therapy

Tuberculosis(TB) is a communicable disease caused by Mycobacterium tuberculosis(M. tuberculosis). WHO estimated that 10.4 million new(incident) TB cases worldwide in year 2016. The increased prevalence of drug resistant strains and side effects associated with the current anti-tubercular drugs make the treatment options more complicated. Hence, there are necessities to identify new drug candidates to fight against various sub-populations of M. tuberculosis with less or no toxicity/side effects and shorter treatment duration. Bacteriocins produced by lactic acid bacteria(LAB) attract attention of researchers because of its "Generally recognized as safe" status. LAB and its bacteriocins possess an effective antimicrobial activity against various bacteria and fungi. Interestingly bacteriocins such as nisin and lacticin 3147 have shown antimycobacterial activity in vitro. As probiotics, LAB plays a vital role in promoting various health benefits including ability to modulate immune response against various infectious diseases. LAB and its metabolic products activate immune system and thereby limiting the M. tuberculosis pathogenesis. The protein and peptide engineering techniques paved the ways to obtain hybrid bacteriocin derivatives from the known peptide sequence of existing bacteriocin. In this review, we focus on the antimycobacterial property and immunomodulatory role of LAB and its metabolic products. Techniques for large scale synthesis of potential bacteriocin with multifunctional activity and enhanced stability are also discussed.

Cloning of Bile Salt Hydrolase Gene and Its Expression in Lactic Acid Bacteria

According to the sequence of the bile salt hydrolase （BSH） gene of Bifidobacterium and the restriction enzyme cutting sites of expression vector pNZ8148, primers were designed and the bile salt hydrolase （BSH） gene was gotten from Bacillus bifidus ATCC 29521 by PCR. BSH gene was inserted into lactic acid bacteria expression vector pNZ8148 to construct the recombinant pNZ8148-BSH. The recombinant pNZ8148-BSH was transferred into lactic acid bacteria NZ9000 with electrotransformation method. And the recombinant which could express BSH protein was obtained. It was identified by SDS-PAGE electrophoresis and activity verification. The result could provide a rationale reference for expressing BSH in lactic acid bacteria.

Isolation and Identification of High-Quality Lactic Acid Bacteria in Forage Corn

[ Objective] To screen suitable lactic acid bacterium strains from forage corn which can be used as silage additives. [ Method] The lactic acid bacterium strains were isolated by inoculation on MRS solid medium containing calcium carbonate, and they were preliminarily identified through morphological, physiological and biochemical experiments. The acid production efficiency was determined. Twelve strains having strong acid-pro- duction ability were selected, and their salt tolerance and acid tolerance were detected. The sequences of their 16 S rDNA were also analyzed. [ Result] A total of 44 lactic acid bacterium strains were isolated from the forage com. As evidenced by the physiological and biochemical experi- ments, the twelve strains having strong acid-production ability belonged to Leuconostoc, Lactobacillus and Enterococcus, respectively, and they had strong salt tolerance and acid tolerance. According to the sequences of 16 S rDNA, A4, B9, B11, B12 and B14 were Lactobacillus plantarum; A1, A2., A7, A11 and B8 were Leuconostoc mesenteroides dextran subspecies; and AB and A9 were Enterococcus hirae. [ Conclusion ] The lactic acid bacterium strains with strong acid-production ability isolated from forage corn can be developed into silage additives.

Antimicrobial Profile of Lactic Acid Bacteria Isolated from Vegetables and Indigenous Fermented Foods of India against Clinical Pathogens Using Microdilution Method

In dairy and food industries lactic acid bacteria （LAB） have been used in form of starter culture that plays vital role in fermentation; as flavouring and texturizing or as preservative agents. There is increasing evidence that lactobacilli which inhabit the gastrointestinal tract develop antimicrobial activities and participate in the host＇s defence system[1]. During fermentation, most of the LAB produces a number of different compounds like organic acids, hydrogen peroxide, diacetyl, acetaldehyde, carbon dioxide, polysaccharides, and proteinaceous compounds called bacteriocins or bacteriocinogenic peptides.

Influence of biofilm-forming lactic acid bacteria against methicillin-resistan Staphylococcus aureus(MRSA S547)

Objective: To investigate the antibacterial effect of selected lactic acid bacteria(LAB)biofilms on the planktonic and biofilm population of methicillin-resistant Staphylococcus aureus(MRSA)(S547).Methods: In this study, biofilm-forming LAB were isolated from tairu and kefir. Isolate Y1 and isolate KF were selected based on their prominent inhibition against test pathogens(using spot-on-agar method and agar-well-diffusion assay) and efficient biofilm production(using tissue culture plate method). They were then identified as Lactobacillus casei(L. casei) Y1 and Lactobacillus plantarum(L. plantarum) KF, respectively using16 S r DNA gene sequencing. The influence of incubation time, temperature and aeration on the biofilm production of L. casei Y1 and L. plantarum KF was also investigated using tissue culture plate method. The inhibitory activity of both the selected LAB biofilms was evaluated against MRSA(Institute for Medical Research code: S547) using L. plantarum ATCC 8014 as the reference strain.Results: L. casei Y1 showed the highest reduction of MRSA biofilms, by 3.53 log at48 h while L. plantarum KF records the highest reduction of 2.64 log at 36 h. In inhibiting planktonic population of MRSA(S547), both L. casei Y1 and L. plantarum KF biofilms recorded their maximum reduction of 4.13 log and 3.41 log at 24 h, respectively. Despite their inhibitory effects being time-dependent, both LAB biofilms exhibited good potential in controlling the biofilm and planktonic population of MRSA(S547).Conclusions: The results from this study could highlight the importance of analysing biofilms of LAB to enhance their antibacterial efficacy. Preferably, these protective biofilms of LAB could also be a better alternative to control the formation of biofilms by pathogens such as MRSA.

Lactic acid bacteria mediated fermented soybean as a potent nutraceutical candidate

Objective: To study some soybean cultivars commonly used in Northern Thailand that exhibit high nutritional profile and to investigate the changes in bioactive principles and antioxidant capacity of the fermented soy broth that was prepared using the selected soybean cultivar and Lactobacillus paracasei HII02 mediated fermentation process.Methods: The best soybean cultivar was subjected to fermentation, and then analyzed the phytochemical, antioxidant and nutritional changes by high performance liquid chromatography and spectrophotometric analysis.Results: Sor Jor 2 soybean cultivar showed rich nutritional profile and was subjected to fermentation process. Lactobacillus paracasei HII02 mediated fermentation of Sor Jor 2 soybean exhibited stable physical and chemical characteristics. Lactic acid bacteria mediated fermentation also increased the aglycone forms of isoflavone content, exhibited antioxidant capacity and thereby enhanced the quality of the fermented soy broth. It also prevented the growth of coliforms in fermented soybean.Conclusions: The study results suggest that fermented soybean is rich in nutrition and considered to be safe for consumption for the improvement of health and to treat the malnutrition.

Antifungal Activity of Lactic Acid Bacteria, Isolated from Bulgarian Wheat and Rye Flour

The economic losses and the health hazards of the mycotoxins produced by spoilage fungi are the main concerns of the food industry. The spoilage of bakery products by fungi is more common in countries with a high humidity and temperature. About 5-10% of food production is spoiled by the growth of yeast and fungi in food materials. Similarly, in Western Europe, the growth of the spoilage fungi of bread is estimated to reach more than 200 million Euros per year. The history conditions of the food can be a major factor in determining any fungal spoilage--for example, stored and processed foods are more sensitive to spoilage when compared with fresh and prepared foods. Lactic acid bacteria isolated from Bulgarian wheat and rye flour were used in the present study to check their antifungal properties against pathogenic yeast and fungi imperfecta using standard disc diffusion method in vitro. A broad spectrum of antifungal activity of the six newly identified as L. plantarum strains e Tsl, Ts2, Ts3,Ts4 and Ts5, and L. helveticus Ts6 was estimated. Our in vitro studies were performed with wheat and rye sourdough, in order to simulate a real product and to assess the bio-protective potential of the tested lactobacilli. The used test-cultures are representatives of carcinogenic, toxigenic, deteriorative and allergenic fungi from the genera .4spergillus and Penicillium. The all tested strains completely suppress the growth of against C. glabrata 72. Strains L. plantarum Tsl and Ts3 completely suppress the growth against S. cerevisae. While, in the sample with L. plantarum strains e Tsl, Ts2, Ts3,Ts4 and Ts5, and L. helveticus Ts6, a retarded and weak growth of A. niger and P. claviforme was observed. However, the spore germination and the colony growth started only on the fifth day of the mould lactobacilli co-cultivation, which also should be considered as a good result. In this study six isolates Tsl,Ts2, Ts3, Ts4, Ts5 and Ts6, from the traditional Bulgarian wheat and rye flour have been identified as L. plantarum and L. helveticus and characterized as cultures with promising antifungal activity. Obtained results from the combined molecular identification （16S rRNA gene sequencing） approach contribute to give new data on the microbial biodiversity of this not well-studied niche. The antifungal activity of our new isolates, identified as L. plantarum and L. helveticus, seems to be a promising advantage of these six strains, suggesting their potential applications in different food technologies. However, more experiments have to be conducted to clarify the nature and the mechanisms of the reported antifungal activity and they are still in progress. The combination of dairy origin and strong inhibitory activity of the lactobacillus strains is a prerequisite for their possible application as starters and/or bioprotective antifungal adjuncts.

Fermented Goat Milk and Cow Milk Produced by Different Starters of Lactic Acid Bacteria： Quality Studies

Lactic acid bacteria （LAB） is widely used as culture starters in dairy fermentation. The aim of this study was to investigate the quality of fermented goat milk and cow milk, as well as the viability of LAB in the same products. Fermentations were performed with pasteurized goat milk or cow milk added with skim milk （18% of solids） using three separately different starters; yoghurt starter （a combination of Streptococcus thermophilus FNCC-0040 and Lactobacillus bulgaricus FNCC-0041）, single starter of Lactobacillus acidophilus FNCC-0029 and Lactobacillus casei FNCC-0051. The parameters observed were pH, acidity, nutritional quality including protein, fat and lactose content and product＇s viscosity. Acidity, pH and viability of LAB were also monitored during storage at refrigerated temperature （4 ℃） for 28 days. Results show that the different LAB starters did not affect the pH, acidity, lactose and protein content. Differences on LAB starters affected fat content and viscosity. The highest score of viscosity （30.00 Pa.s ± 7.02 Pa.s） was observed on products fermented by yoghurt starters, followed by products obtained using starter of L. acidophilus （17.7 ±11.4） and L. casei （8.62 ±0.35）. Protein content, acidity, pH and viscosity were not significantly different between products obtained from goat milk and cow milk. Fat content in fermented goat milk was higher （5.03% ±0.62%） than in fermented cow milk （3.52% ±0.37%）, however, lactose content was higher in fermented cow milk （5.16% ±0.40%） than in fermented goat milk （4.53% ±0.35%）. Total LAB concentration in fermented cow milk during storage was 8.03± 0.52 logt0 cfu/mL, while in fermented goat milk was 7.81 loglo cfu/mL ± 0.67 loglo cfu/mL. There was a 10.83% decrease in LAB viability in fermented cow milk and 11.40% in fermented goat milk after 28 days of storage. In conclusion, quality of fermented milk is affected by the starters applied, raw milk source and storage period.

Application of Metabonomics in the Research of Lactic Acid Bacteria-fermented Foods

Lactic acid bacteria have been important industrial floras in the food fermentation production industry since ancient times.Their metabonomics technology has been widely used in the process monitoring,product classification and flavor formation mechanism of lactic acid bacteria-fermented foods.In this study,we discussed the application status of metabonomics technology in lactic acid bacteria-fermented food industry and scientific research,including dairy products,soy products,beverages and some pickled foods.Metabolomics will be applied in the research fields of lactic acid bacteria metabolism mechanism of lactic acid bacteria-fermented foods,lactic acid bacteria metabolomics database construction and expansion,metabolomics and genomics,and proteomics.In particular,the metabolomics technology will be introduced into product development and quality monitoring of traditional Chinese lactic acid bacteria-fermented foods,such as fermented bean curd and suancai,thereby perfecting industry norms and improving the level of industry development.

Inhibitory Activities of Lactic Acid Bacteria against Multi-Drug Resistant Uropathogenic <i>Staphylococcus saprophyticus</i>Isolated from Symptomatic Women in Lagos, Nigeria

The uropathogenic Staphylococcus saprophyticus is reported severally to be resistant to the drugs often used empirically for treatment of urinary tract infections (UTIs). Their ability to exhibit resistance to multiple drugs is a great deal of threat to successes recorded in the management of UTIs caused by this pathogen. Lactic acid bacteria (LAB) have been demonstrated to exhibit antimicrobial activities but studies about their prospect against multi-drug resistant S. saprophyticus are quite few. This study therefore investigated activities of LAB against the multi-drug resistant S. saprophyticus recovered from urine samples of symptomatic women. The three different species of LAB (Lactobacillus fermentum BTA 62, Lactobacillus johnsonii BTA 86 and Weissella confusa BTA 40) previously isolated and identified by 16S rRNA sequencing were selected based on their history of antimicrobial activities. Their metabolites were employed in the antagonistic assays against six (6) multi-drug resistant test pathogens recovered from urine samples of symptomatic, non-pregnant women attending clinics in Lagos, Nigeria and the control (S. saprophyticus subs bovis strain DSM 18669) following standard procedures. The pathogens showed resistances to almost all the antibiotics except levofloxacin, ciprofloxacin, imipenem while the control showed resistance to three. The LAB, L. fermentum inhibited five (83.3%) of the pathogens with zone diameter of 12 - 17 mm, followed by W. confusa inhibiting three (50%) with 15 - 17 mm. Lactobacillus johnsonii on the other hand, inhibited a pathogen and the control with zones of 13 mm and 14 mm respectively. In conclusion, the extracted metabolites of LAB inhibited the growth of multi-drug resistant clinical isolates of uropathogenic S. saprophyticus and may therefore be potent alternatives to antibiotics.

Antioxidant Activities of Exopolysaccharides Produced by Lactic Acid Bacteria Isolated from Commercial Yoghurt Samples

An antioxidant is a substance that inhibits the oxidation of other molecules caused by free radicals. The inbuilt antioxidant systems possessed by living organisms are generally not enough to prevent them from oxidative damages and the uses of synthetic antioxidants also have some harmful effects. This study was aimed at evaluating the antioxidant activities of exopolysaccharides produced by lactic acid bacteria isolated from yoghurt. Lactic acid bacteria (LAB) were isolated from six different brands of commercially available yoghurt using deMan Rogosa Sharpe (MRS) agar. The LAB isolates were identified based on morphological and biochemical analyses and were screened for exopolysaccharide (EPS) production. The LAB isolates screened positive were used for EPS production in a liquid medium and the EPS produced were purified and quantified using standard methods. Antioxidant activities of the EPS were evaluated by determining the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, ferric ion reducing power, and total phenolic contents. Data obtained were analysed using Analysis of Variance. Total lactic acid bacterial count obtained from the yoghurt samples ranged from 0 - 3.9 × 104 CFU/mL with sample A (Fan Yoghurt) having the highest LAB count (3.9 × 104 CFU/mL). The isolated LAB and their incidence rate were Lactobacillus plantarum (25.49%), L. delbrueckii (19.61%), L. fermentum (15.69%), L. acidophilus (13.73%), Leuconostoc mesenteroides (11.76%), Lactococcus lactis (7.84%), and Lactobacillus casei (5.88%). Fifty-one out of the 64 LAB isolates were screened positive for EPS production and only six were able to produce substantial quantity of EPS ranging from 127.4 - 208.5 mg/L. The exopolysaccharides produced by L. fermentum had the highest DPPH radical scavenging activity (62.90%) while that of L. plantarum had the lowest (23.10%) at a concentration of 1000 μg/mL. Also, the EPS produced by L. fermentum recorded the highest ferric ion reducing power (12.89 mg AAE/mL) at 1000 μg/mL while that of L. plantarum had the lowest (5.62 mg AAE/mL). At 1000 μg/mL, the total phenolic contents of the EPS samples ranged from 1.41 - 1.58 mg GAE/mL, and the EPS produced by L. fermentum had the highest (1.58 mg GAE/mL) while those produced by L. paracasei had the lowest (1.41 mg GAE/mL). This study revealed that the exopolysaccharides produced by the LAB isolates showed high antioxidant activities with respect to their DPPH free radical scavenging activity, ferric ion reducing power and total phenolic contents.