Co-culture fermentation of peanut-soy milk for the development of a novel functional beverage

Most of the commercial probiotic products are dairy-based, and the development of non-dairy probiotic products could be an alternative for new functional products. The peanut-soy milk (PSM(1)) was inoculated with six different lactic acid bacteria (LAB), including probiotic strains and yeasts and fermentation was accomplished for 24h at 37 °C and afterwards, another 24h at ±4 °C. The Pediococcus acidilactici (UFLA BFFCX 27.1), Lactococcus lactis (CCT 0360), Lactobacillus rhamnosus (LR 32) probiotic LAB, and the Lactobacillus delbrueckii subsp. bulgaricus (LB 340) yogurt starter culture reached cell concentrations of about 8.3log CFU/mL during fermentation. However, these strains were not able to acidify the substrate when inoculated as pure culture. The Lactobacillus acidophilus (LACA 4) probiotic produced significant amounts of lactic acid (3.35 g/L) and rapidly lowered the pH (4.6). Saccharomyces cerevisiae (UFLA YFFBM 18.03) did not completely consume the available sugars in PSM and consequently produced low amounts of ethanol (0.24 g/L). In pure culture, S. cerevisiae (UFLA YFFBM 18.03), L. rhamnosus (LR 32), L. acidophilus (LACA 4), and P. acidilactici (UFLA BFFCX 27.1) promoted the increase of total amino acids (48.02%, 47.32%, 46.21% and, 44.07%, respectively). However, when in co-cultured, the strains consumed the free amino acids favoring their growth, and reaching the population of 8log CFU/mL in PSM. Lactic acid production increased, and 12 h was required to reach a pH value of 4.3. In general, the strains were more efficient in the use of available carbohydrates and release of metabolites in co-cultured than in single culture fermentations. An average of 58% and 78% of available carbohydrates was consumed when single and co-cultures were evaluated, respectively. Higher lactic acid contents were found in a binary culture of P. acidilactici (UFLA BFFCX 27.1) and L. acidophilus (LACA 4), and by co-culture of P. acidilactici (UFLA BFFCX 27.1), L. acidophilus (LACA 4) and S. cerevisiae (UFLA YFFBM 18.03) (9.03 and 8.51 g/L, respectively). The final content of ethanol was 0.03% (v/v) or less, which classified the final beverage as non-alcoholic.