Passion fruit by-product and fructooligosaccharides improve the growth and folate production by Streptococcus thermophilus in co-culture with probiotic lactobacilli strains during soymilks fermentation after tri-enzyme treatment

SAAD, S.M.I.; ALBUQUERQUE, M.A.C.; BEDANI, R.; LEBLANC, JEAN GUY

Conferencia; International Scientific Conference on Probiotics and Prebiotics - IPC2017; 2017

IntroductionSoy-based products are an alternative to the consumption of dairy products not only by individuals who present allergy and/or intolerance to milk but also by people with vegetarian habits. However, soy products possess unsavoury and anti-nutritional factors that could be improved by the use of lactic acid bacteria (LAB) during fermentative processes. Besides, it is known that the processing of soybeans may cause the loss of some water soluble nutrients such as folate, a B-group vitamin, and that some folate producing LAB might be used to bio-enrich fermented soymilks. Thus, the ability of two Streptococcus thermophilus (ST-M6 and TH-4) in co-culture with two commercial probiotic lactobacilli (Lb. acidophilus LA-5 and Lb. rhamnosus LGG) to grow and produce folates during fermentation of four soymilk formulations was evaluated.MethodsFour soymilk formulations (soymilk (SM); SM with 1% (m/v) of passion fruit by-product (PF); SM with 1% of fructooligosaccharides (FOS); SM with 0.5% of PF and 0.5% of FOS) was fermented by two Streptococcus thermophilus (ST-M6 and TH-4) in co-culture with two commercial probiotic lactobacilli (Lb. acidophilus LA-5 and Lb. rhamnosus LGG). Each strain (4-5 log cfu/ml) was inoculated in each SM formulation (ST-M6+LA-5, ST-M6+LGG, TH-4+LA-5 and TH-4+LGG) and incubated at 37 °C for 24 h. Samples were taken at 0 and 24 h to count the viable cells and treated enzymatically with amylase, protease and human plasma and the folate content determined using a microbiological assay.Results All strains reached counts higher than 7 log UFC/mL in all SM formulations after 24h of fermentation. Each non inoculated soymilk (control) presented the following folate values: SM (602 ± 63 ng/mL), SM+PF (492 ± 66 ng/mL), SM+FOS (162 ± 34 ng/mL), and SM+PF+FOS (346 ± 7 ng/mL). Only the co-culture TH-4+LA-5 (675±15 ng/mL) was able to produce folate in SM formulation and all co-cultures were able to produce folate in SM supplemented with PF, FOS and PF with FOS. The highest folate production was observed in SM+FOS fermented by the co-culture ST-M6+LGG (1112 ± 51 ng/mL).DiscussionThis study showed that the presence of passion fruit by-product and FOS stimulates not only the growth of the microorganisms in co-culture but also improves the folate production. Studies indicate that Streptococcus thermophilus strains are good folate producers while lactobacilli strains are known to be consumers of the vitamin. However, previous studies showed that both Lb. acidophilus LA-5 and Lb. rhamnosus LGG are able to produce folate during the fermentation of a culture media supplemented with fruit by-products. The folate production in this study was strain dependent and also influenced by the composition of each soymilk.