Bifidobacteria as Potential Functional Starter Cultures: A Case Study by MSc Students in Food Science and Technology (University of Foggia, Southern Italy)

This research paper was the results of activity of MSc students of Food Science and Technology, attending the class “Biotechnology of Functional Starter”. Five strains of bifidobacteria (Bifidobacterium animalis subsp. lactis;B. longum subsp. infantis;B. breve;B. animalis subsp. animalis;B. bifidum) were evaluated in order to assess their suitability as functional starter cultures, by studying the following technological and probiotic traits: growth at different temperatures, NaCl amounts and pH values;acidifying ability;metabolism (arginin deamination, esculin hydrolysis, acetoin production);survival at low pH and in presence of bile salts;hydrophobic properties;antibiotic resistance. After laboratory assays and strain selection through a multivariate analyses, it was highlighted that B. longum subsp. infantis and B. animalis subsp. lactis represent a good compromise as potential functional starter cultures, as B. animalis subp. lactis showed a high growth index at pH 5 and good values at 25?C and 30?C, as well as the minimal viability loss at pH 2.5. B. longum subsp. infantis DSMZ 20088 was the best microorganism for its growth index in presence of 6.5% of salt added and at 25?C and 30?C.

Functional Starter Cultures for Meat: A Case Study on Technological and Probiotic Characterization

The selection of a starter is a complex process, involving different steps, like a preliminary characterization under laboratory conditions, the selection of the most promising strains, a lab validation and the final validation in a large-scale fermentation;the selection of a functional starter includes a further step, dealing with the assessment of the functional traits. This paper proposes a case study on how use a step-by-step approach, based on some rapid protocols, to select promising starter cultures with probiotic abilities. Nine strains, isolated from a commercial preparation, were studied in relation to some enzymatic activities (slime and acetoin production, reduction of nitrates, proteolytic activity and hydrolysis of tributyrin), technological (acidification and growth at different temperatures, pHs and salt amounts) and probiotic traits (hydrophobicity, co-aggregation towards Salmonella sp. and Escherichia coli, survival at pH 2.5 and in presence of bile salts, antibiotic resistance) and compared to some collection isolates. As a final step, a multivariate approach was used to select the most promising isolates. The isolates from the commercial preparation were able to perform the fermentation (e.g. acidification) at low temperatures with some interesting traits in terms of bioactivity towards E. coli O157:H7, whilst some interesting probiotic traits in terms of hydrophobicity and survival in conditions that mimicked the gut were found for the collection isolates.

Use of Starter Cultures in Olives: A Not-Correct Use Could Cause a Delay of Performances

The role of lactic acid bacteria for a correct course of fermentation of table olives has been extensively reviewed and it is a common idea that the inoculum of selected strains could exert a strong benefit for product quality;however, the basic assumption of this research is that a not-correct preparation of starter could affect its performances in brines and delay the benefit of a starter inoculum. Thus, some selected strains of LAB (lactic acid bacteria) and yeasts were inoculated into brines of Bella di Cerignola olives (Spanish style), as a single starter (LAB or yeasts) or a combined preparation (LAB + yeasts) and compared to a natural fermentation, focusing on the performances of the process (acidification, production of lactic acid) and trying to verify the basic assumption. LAB and yeasts were grown in the opportune lab media and then directly inoculated in brine after the lye treatment. LAB exerts a kind of benefit (increased content of lactic acid) only for 2 - 3 weeks;then, the inoculated samples behave in the same way as not-inoculated ones. Thus, this research underlined that a starter culture, not prepared in the correct way, could not be useful to guide the fermentation.

Comparison of Direct Microbial Count Procedures for Planktonics and Sessiles Enumeration

In the present investigation, the sensitivity of different direct microbial count procedures applied on systems containing both planktonics and sessiles was tested. The direct count pour plate was compared with direct epifluorescent microscopic enumerations in order to evaluate the efficiency of the studied techniques in giving information about microbial activity or viability. Our results indicate that the standard plate count procedure is the most sensitive method to estimate viable and cultivable planktonic cells. On the other hand, direct enumeration by epifluorescent microscopy may become an interesting alternative to count sessile cells.

Functional Characterization of Bifidobacteria of Human Origin: A Case Study by the Students of Food Science and Technology of the University of Foggia (Southern Italy)

The aim of this paper was to study the potential technological and probiotic properties of bifidobacteria isolated from human feces. Bifidobacteria, naturally present in the dominant colonic microbiota, represent up to 25% of the cultivable faecal bacteria in adults and 80% in infants. Bifidobacteria have been shown to adhere and colonize in high numbers different types of cultured intestinal epithelial cells;moreover some authors reported that some strains are able to stabilize the intestinal microbiota during and after antibiotic therapy, modulate the immune system, protecting against chemically induced intestinal inflammation and reducing symptoms of colitis. Eight isolates of bifidobacteria were studied to assess their technological and probiotic traits;the technological characterization relied on the assessment of enzymatic activities (proteolytic and lipolytic activity), growth under various conditions (pH, temperature and addition of salt), acidifying ability and metabolism (arginine deamination, esculin, esculin hydrolysis and citrate metabolism). The study of the probiotic characteristics focused on the evaluation of the survival at low pH and with bile salts added, antibiotic resistance, and hydrophobic properties. As a result of this process, two promising strains were selected for further studies.