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.

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.

The Optimized Synthesis of Starch-g-Lactic Acid Copolymer with High Grafting Degree Catalyzed by Sulfuric Acid

The starch-g-lactic acid copolymer was synthesized with catalysis of sulfuric acid by onestep process, and the structure of starch-g-lactic acid copolymer was characterized by means of IR, 13C-NMR, HMBC, XRD, and SEM. The experimental results show that the maximum grafting degree of starch can reach 75% when the starch-g-lactic acid copolymer is activated at 80 ℃ for 2 h and reacted with lactic acid at 90 ℃ for 4 h in vacuum.

Effect of Starch/Polylactic Acid Ratio on the Interdependence of Two-Phase and the Properties of Composites

Starch/polylactic acid(PLA) composites were prepared by melt extrusion, with corn starch and PLA as raw materials, glycerol as the plasticizer. Effects of starch/PLA ratio on the interdependence of two-phase and other properties of the composites were studied. The combination of results of TGA with SEM indicated that the interdependence between starch and PLA was increased gradually as the starch/PLA ratio reduced. DSC results showed that the glass transition temperature(Tg), melting temperature(Tm) and degree of crystallinity of PLA in composites were increased gradually, whereas the cold crystallization temperature(Tc) was gradually decreased as the starch/PLA ratio reduced. The rheological properties of composites were closely related with the interdependence of two-phase, with reducing starch/PLA proportion, the interdependence was increased, and then the strain for storage modulus was firstl reduced and then gradually increased. Frequency scanning showed that the storage modulus and complex viscosity were decreased with reducing starch content. As the starch/PLA ratio reduced, the matrix phase PLA was increased, so that the strength of composites was increased gradually, whereas water absorption rate was decreased gradually.

Blends of Poly(lactic acid) with Thermoplastic Acetylated Starch

Blends of poly（lactic acid）（PLA） and thermoplastic acetylated starch（ATPS） were prepared by means of the melt mixing method. The results show that PLA and ATPS were partially miscible, which was confirmed with the measurement of Tg by dynamic mechanical analysis（DMA） and differrential scanning calorimetry（DSC）. The mechanical and thermal properties of the blends were improved. With increasing the ATPS content, the elongation at break and impact strength were increased. The elongation at break increased from 5% of neat PLA to 25% of the blend PLA/ATPS40. It was found that the cold crystallization behavior of PLA changed evidently by addition of ATPS. The cold crystallization temperature（Tcc） of each of PLA/ATPS blends was found to shift to a lower temperature and the width of exothermic peak became narrow compared with that of neat PLA. The thermogravimetry analysis（TGA） results showed that the peak of derivative weight for ATPS moved to higher temperature with increasing PLA content in PLA/ATPS blends. It can be concluded that PLA could increase the thermal stability of ATPS. The rheological measurement reveals the melt elasticity and viscosity of the blends decreased with the increased concentration of ATPS, which was favorable to the processing properties of PLA.

Effects of applying lactic acid bacteria to the fermentation on a mixture of corn steep liquor and air-dried rice straw

This study was to determine the fermentation quality of a mixture of corn steep liquor(CSL)(178 g/kg wet basis) and air-dried rice straw(356 g/kg wet basis) after being treated with inoculants of different types of lactic acid bacteria(LAB). The treatments included the addition of no LAB additive(control),which was deionized water; homo-fermentative LAB alone(^(ho)LAB), which was Lactobacillus plantarum alone), and a mixture of homo-fermentative and hetero-fermentative LAB(^(he+ho)LAB), which were L. plantarum, Lactobacillus casei, and Lactobacillus buchneri. The results showed that the inoculation of the mixture of CSL and air-dried rice straw with ^(he+ho)LAB significantly increased the concentration of acetic acid and lactic acid compared with the control(P < 0.05). The addition of ^(he+ho)LAB effectively inhibited the growth of yeast in the silage. The concentration of total lactic acid bacteria in the ^(he+ho)LAB-treated silage was significant higher than those obtained in other groups(P < 0.05). The duration of the aerobic stability of the silages increased from 56 h to >372 h. The control group was the first to spoil, whereas the silage treated with ^(he+ho)LAB remained stable throughout the 372 h period of monitoring. The results demonstrated that the ^(he+ho)LAB could effectively improve the fermentation quality and aerobic stability of the silage.

Effect of Application of a Bacteria Inoculant and Wheat Bran on Fermentation Quality of Peanut Vine Ensiled Alone or with Corn Stover

To find an effective method for ensiling peanut vine （PV）, fermentation characteristics and nutritional values of PV silage and the mixture of PV with corn stover （CS） silage in a ratio of 1 ： 1 fresh weight, prepared by adding lactic acid bacteria （LAB）, 10% wheat bran （WB） and LAB＋WB at ensiling were evaluated in 2009 and 2010. The fermentation qualities of PV silage ensiled with the LAB and WB additives were improved compared with those of the control （PV ensiled alone）. However, the pH did not decline to the critical level of 4.2, and the nutritional values of the silage were not protected against losses in the LAB and WB addition silages. Ensiling PV in mixture with CS generated optimal moisture content and buffering capacity （BC） of ensiled materials. After adding the LAB and WB additives to mixture silage, especially adding LAB＋WB, the fermentation qualities and nutritional values of the mixture silage were improved significantly （P〈0.05）, and the Flieg＇s score reached to 99. The result suggested that it is a feasible method to ensile the mixed materials of PV with CS by adding LAB and high concentration of water soluble-carbohydrate materials for providing a good fermentation quality of PV silage.

Addition of Thermoplastic Starch(TPS)to Binary Blends of Poly(lactic acid)(PLA)with Poly(butylene adipate-co-terephthalate)(PBAT):Extrusion Compounding,Cast Extrusion and Thermoforming of Home Compostable Materials

Development of home compostable materials based on bioavailable polymers is of high strategic interest as they ensure a significant reduction of the environmental footprint in many production sectors.In this work,the addition of thermoplastic starch to binary PLA/PBAT blends was studied.The compounds were obtained by a reactive extrusion process by means of a co-rotating twin screw extruder.Thermomechanical,physical and chemical characterization tests were carried out to highlight the effectiveness of the material design strategy.The compounds were subsequently reprocessed by cast extrusion and thermoforming in order to obtain products suitable for the storage of hot food.The extruded films and the thermoformed containers were further characterized to highlight their thermo-mechanical,physical and chemical properties.Thermo-rheological,mechanical and physical properties of the material and of the cast film were analyzed thoroughly using combined technique as capillary rheometer,MFI,DSC,VICAT/HDT,XRD,FTIR,UV-Vis,SEM,permeability and,lastly,running preliminary chemical inertness and biodegradation tests.Particular attention was also devoted to the evaluation of the thermo-mechanical resistance of the thermoformed containers,where the PLA/PBAT/TPS blends proved to be very effective,also presenting a high disintegration rate in ambient conditions.

Modulating of food glycemic response by lactic acid bacteria

There are some strategies for modulating the glycemic response of food through synthesized metabolites such as organic acids,fatty acids,sugar alcohols,bioactive peptides,and exopolysaccharides by bacteria,yeast,and/or fungi during fermentation.The different species of lactic acid bacteria (LAB) are the most important option in fermented food production because they are considered food-grade,their products can be directly used in food,their usability of a cheap and wide range of substrate,and suitable for genetic modification.They can contribute to lowering the glycemic load of nutrition through their organic acid,alcohol,polysaccharides,and vitamin production.This study aimed to review the effects of lowering the glycemic responses of foods by LAB via metabolites produced and their contribution to human well-being in this way.

Use of Poly-Lactic Acid (PLA) to Enhance Properties of Paper Based on Recycled Pulp

Nowadays, recycled paper is broadly used due to environmental reasons. Furthermore, the addition of starch as a dry strength additive improves the properties of recycled paper. Poly-Lactic Acid (PLA), a product from bio-refinery process, has recently been shown to act as a promising strength additive that could be used in combination with starch to further improve the strength of paper. In this study, the use of PLA of three molecular weights (MW) in combination with four different starches was investigated. Three recycled pulps from different origins, with the kappa number of 27.9 to 66 were used. Paper handsheets were made, and selected paper properties were tested. The results indicate that handsheets properties were influenced by the MW of PLAs, the type of starch used, and the lignin content of the pulp. The paper handsheets made from lignin-rich pulp (pulp A, kappa number 66), combined with 0.1% medium MW PLA (PLA_1) and 0.9% cationic starch containing 0.43% N gave the highest improvement for tensile strength, wet tensile strength, air and water resistance. This result verifies that a higher kappa number pulp has better attraction to the hydrophobic PLA. Moreover, the higher charge cationic starch led to higher tensile strength due to the increase of affinity to the anionic fiber surface. Interestingly, results show that amphoteric starch is a promising substitute for high cationic charge starch when combined with the medium MW PLA to improve tensile strength of paper. This study demonstrated that a starch-PLA blend represents a promising approach in improving properties of recycled paper.

Effect of different levels of corn steep liquor addition on fermentation characteristics and aerobic stability of fresh rice straw silage

The object of this study was to determine the proper mixing ratio of fresh rice straw to corn steep liquor(CSL) to obtain a high protein content silage feed. The following experimental silages were generated: the control(C1), composed of fresh rice straw without CSL additive, mixed with CSL in the ratios of 4:1(C4),3:1(C3) and 2:1(C2). Lactic acid bacteria(LAB) inoculant was applied at the rate of 50 mL/kg(fresh basis)of forage to achieve a final application rate of 1 x 10~6 cfu/g of fresh matter(FM). Duplicate silos for each treatment were opened after 0,3, 7,10,20,30,45 and 60 d for microbiological and chemical analysis. The results showed that the addition of CSL significantly increased crude protein(CP) contents, and decreased neutral detergent fiber(NDF) and acid detergent fiber(ADF) contents of treatments after 60 d of ensiling(P < 0.05). The lactic acid contents in C4 and C3 were significantly higher than that in C1(P <0.05). In summary, mixing fresh rice straw with CSL at addition levels of 4:1(C4) and 3:1(C3) can improve the fermentation quality and nutrient composition of fresh rice straw silage. However, a large proportion of CSL(C3) had a negative impact on the aerobic stability of fresh rice straw.

Directional Breeding of High Itaconic Acid Yielding Strain of <i>Aspergillus terreus</i>with a New Plate Technique

Itaconic acid is commercially produced by the cultivation of Aspergillus terreus using starch hydrolysate as carbon source. The degree of hydrolysis had a great influence on itaconic acid production which was suitable when corn starch was saccharified at 35 DE. The α-amylase was sufficient to drive the starch hydrolysis to the degree. The agar plate assay with LiCl treatment provided a rapid, simple and unequivocal method for screening large numbers of colonies for itaconic acid producing strains. It was learned by experience that the strains on the plates with thick hyphae and light-colored spores often accompanied high itaconic acid production. A strain, designated Ast165, producing itaconic acid with a high yield, was successfully obtained by directional breeding of metabolic end products resistant strains. The itaconic acid concentration produced by Ast165 was 53.8 g/l from 100 g/l of starch hydrolysate in shake flasks. The conversion rate was 61.3%, which was the highest value found in tests.

菌酶协同发酵对玉米蛋白粉消化率的影响研究

研究旨在优化菌酶协同发酵玉米蛋白粉工艺条件,从而提高玉米蛋白粉的消化性。该研究是在酸性蛋白酶、木瓜蛋白酶最优条件作用下,以玉米蛋白粉水溶性蛋白质含量为指标,通过单因素和正交试验确定最佳发酵条件。并对菌酶协同发酵玉米蛋白粉产物的游离巯基含量、二硫键含量、表面疏水性、氨基酸和体外消化率等理化特性进行测定分析。结果表明,最佳发酵条件:乳酸菌发酵料液比1∶4(g∶mL),接种量0.3%,发酵温度39℃,发酵时间24 h。协同发酵处理后,亲水氨基酸含量从32.19 mg/g升高至35.25 mg/g,游离巯基含量由65.43μmol/g升高至88.42μmol/g,体外消化率由60.15%升高至80.42%。综上,菌酶协同发酵可显著增加玉米蛋白粉的体外消化率,具有良好的应用前景。

不同种类添加剂对全株玉米发酵特性及营养品质的影响

试验旨在筛选适用于全株玉米青贮调制的添加剂种类及添加量,促进青贮玉米产业化开发。以蜡熟期全株玉米为原料,研究甲酸、乳酸菌和糖蜜对全株玉米发酵特性、营养品质及有氧稳定性的影响。结果显示:与自然发酵相比,6 mL/kg甲酸可显著降低青贮饲料中不良微生物的数量及氨态氮(NH_(3)-N)含量(P<0.05),提高了可溶性碳水化合物(WSC)含量及有氧稳定性。添加布什乳杆菌或植物乳杆菌+布什乳杆菌复合菌剂可显著增加乙酸含量(P<0.05),降低不良微生物数量及NH_(3)-N含量,提高有氧稳定性。添加糖蜜显著增加了青贮饲料中有害菌的数量及NH_(3)-N含量(P<0.05),降低了乙酸、干物质(DM)和WSC含量。研究表明,综合考虑全株玉米青贮饲料的发酵特性、营养品质及有氧稳定性,生产中推荐采用6 mL/kg甲酸、单独添加布氏乳杆菌或按1∶5配比添加植物乳杆菌与布氏乳杆菌复合菌剂对全株玉米进行青贮。

聚乳酸改性糯玉米淀粉的制备及表征

以糯玉米淀粉为原料、异辛酸亚锡为催化剂,在丙交酯熔融体系中制备了聚乳酸改性糯玉米淀粉。建立了聚乳酸改性糯玉米淀粉取代度的^(1)HNMR测试方法,以取代度为响应值,反应时间、反应温度、丙交酯添加量为考察因素,通过单因素和响应面实验优化了聚乳酸改性糯玉米淀粉的合成工艺,得到最优工艺为:反应时间12.46 h,反应温度111.75℃,丙交酯添加量为淀粉质量的258%,预测最大取代度为0.0253,通过实际操作条件调整后实际取代度为0.0238。对最优条件下制备的聚乳酸改性淀粉进行了系列表征,证实聚乳酸改性糯玉米淀粉的颗粒结构没有被完全破坏,晶型、相对分子质量等性能优于溶剂法传统技术制备的聚乳酸改性糯玉米淀粉。

不同乳酸菌青贮剂对桥单6号全株玉米青贮品质的影响

[目的]为研究自制青贮剂GMDL-25对桥单6号全株玉米青贮品质的影响。[方法]选取蜡熟期桥单6号全株玉米(整株切碎至2 cm)为试验材料,设3个处理组,以自然发酵组为对照组,试验组分别添加自制青贮剂GMDL-25和市售乳酸菌青贮剂,装入青贮袋后经真空密封于避光阴凉处发酵2个月左右。每个处理3个重复,每个重复1袋。发酵完成后,进行感官评定,测定微生物数量、氨态氮含量、pH值和营养成分。[结果]自制GMDL-25处理组全株玉米青贮料有较强的芳香味,色泽与原料颜色相近,感官指标评分为20分,得分最高。乳酸菌数量为78.00 log CFU/g,与自然发酵组相比,乳酸菌数量显著增加(P<0.05)。[结论]桥单6号全株玉米添加GMDL-25乳酸菌制剂进行发酵,可明显提高感官指标和乳酸菌数量,保持良好的青贮品质。

制备工艺对高直链玉米淀粉—硬脂酸复合物性质的影响

[目的]优化高抗性淀粉(RS)含量的淀粉—脂质复合物制备工艺,探究工艺参数对复合物抗消化性的影响。[方法]采用单因素试验和正交设计研究了高直链玉米淀粉(HA)预处理及其与硬脂酸(SA)络合过程中温度和时间参数对复合物RS含量的影响,分析最优工艺制备的HA-SA复合物的理化性质、抗消化性及水合特性。[结果]在糊化温区继续升高预处理温度、延长预处理时间、络合温度高于75℃均导致RS含量显著降低(P<0.05);HA-SA复合物最优制备工艺为:HA经85℃的退火温度预处理12 h后,在75℃与SA络合90 min;所制备的HA-SA具有V型晶体特征、完整的淀粉颗粒,为Ⅰ型淀粉—脂质复合物;与HA相比,其热稳定性、抗消化性显著升高,但膨胀力显著降低(P<0.05)。[结论]退火温度预处理和适宜的络合温度有利于HA-SA中RS组分的形成;预处理过程中加热强度的增加使淀粉过度糊化,阻碍了直链淀粉与脂质的络合,络合过程中过高的温度也导致复合物中RS组分的解离,使RS含量降低;退火预处理使HA保留了完整的颗粒结构,是HA-SA抗消化性高的原因之一。

乳酸菌对不同果穗状态全株青贮玉米饲料品质的影响

为研究乳酸菌添加剂对不同果穗状态全株玉米青贮饲料发酵品质、营养品质、真菌污染和有氧稳定性的影响,利用蒸馏水(CK)、植物乳杆菌处理(LP处理,添加量为1×10^(6)CFU/g鲜样)以及布氏乳杆菌处理(LB处理,添加量为1×10^(6)CFU/g鲜样)添加进果穗全包、果穗露顶和果穗露顶穗腐组中进行青贮发酵。结果表明,所有处理均取得了良好的发酵效果。果穗露顶组具有更高的WSC含量和霉菌数量,且相对果穗全包组具有更高的总酸含量、乳酸/乙酸比值和更低的pH。LP处理增加了乳酸含量、降低了pH。LB处理显著增加了乙酸含量并降低乳酸/乙酸比值,具有最低的酵母菌数量和最高的有氧稳定性,2种添加剂的使用均显著降低了氨态氮含量和霉菌数量。乳酸菌添加剂的应用对于提升不同果穗状态的全株玉米青贮饲料发酵品质、营养品质和有氧稳定性并降低真菌污染具有重要意义。

乳酸菌和纤维素酶对马蹄渣和玉米蛋白粉混合青贮饲料品质及体外瘤胃发酵特性的影响

本试验旨在评价不同添加剂对马蹄渣和玉米蛋白粉混合青贮饲料发酵品质、化学成分、微生物数量和体外瘤胃发酵特性的影响。将马蹄渣和玉米蛋白粉按照76∶24的比例混合均匀作为青贮原料,在青贮时分别进行如下处理:1)不添加乳酸菌和纤维素酶(CON组);2)添加1×108CFU/g乳酸菌(LAB组);3)添加50 U/g纤维素酶(CE_(50)组);4)添加100 U/g纤维素酶(CE100组);5)添加1×108CFU/g乳酸菌+50 U/g纤维素酶(LAB+CE50组);6)添加1×108CFU/g乳酸菌+100 U/g纤维素酶(LAB+CE_(100)组)。每组设3个重复,每个重复设2个平行。混合青贮60 d后打开青贮袋取样进行分析。结果显示:在化学成分方面,与CON组相比,青贮时组合添加乳酸菌和纤维素酶可以显著降低混合青贮饲料的中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、酸性洗涤木质素(ADL)、纤维素、半纤维素含量(P<0.05),同时显著提高粗蛋白质(CP)含量(P<0.05),其中以LAB+CE100组最高。发酵品质方面,LAB、LAB+CE50以及LAB+CE100组混合青贮饲料的pH及氨态氮(NH3-N)含量与CON组相比显著降低(P<0.05),同时乳酸和乙酸含量与CON组相比显著升高(P<0.05),且以LAB+CE100组最高;单独添加乳酸菌或组合添加乳酸菌与纤维素酶均可显著提高混合青贮饲料中乳酸菌的数量(P<0.05),并降低不良细菌数量或抑制不良细菌的增殖。在体外产气方面,随着发酵时间的延长,各组的产气量不断升高,其中LAB+CE100组的产气速率、48 h产气量最高。在体外瘤胃发酵参数方面,各组发酵液pH均在6.56~6.84,且与发酵时间呈负相关趋势;各添加剂组发酵液中总挥发性脂肪酸、乙酸、丙酸、丁酸含量与CON组相比均显著增加(P<0.05);添加乳酸菌的各添加剂组发酵液中乙酸/丙酸比值与CON组相比显著降低(P<0.05)。由此可见,组合添加乳酸菌和纤维素酶可改善马蹄渣和玉米蛋白粉混合青贮饲料的品质和体外瘤胃发酵特性,其中以添加1×108CFU/g乳酸菌+100 U/g纤维素酶的效果最好。

玉米破碎度与发酵条件对玉米全粉发酵及产品加工特性的影响

以硬质玉米籽粒为原料,通过控制玉米破碎度调控乳酸菌发酵过程,制备高黏弹性玉米全粉。以发酵玉米全粉所制面团的质构特性为指标,确定玉米籽粒破碎度,后通过单因素和正交试验以玉米全粉所制面团黏附性为指标优化发酵工艺,分析发酵前后玉米全粉的加工特性。研究结果表明,玉米籽粒破碎辊轮间距为1.6 mm时,能够有效控制发酵过程;在此条件下,玉米发酵条件为发酵时间22 h、发酵温度37℃、料液比1∶2.5(g/mL)、接种量0.4%(质量分数),该工艺发酵玉米全粉所制面团黏附性为0.733 1 N·mm。经发酵处理后,玉米全粉持水性提升22.44%(P<0.05),玉米全粉分散液的弹性模量(G′)和黏性模量(G″)明显提高;玉米全粉所制面团的质构特性显著改善(P<0.05),其中面团黏附性、内聚性、弹性、胶黏性和咀嚼性分别提高45.73%、33.33%、29.11%、43.40%和102.73%,硬度下降5.10%。