A rapid pH value drop in the PSM substrate was observed by
L. acidophilus (LACA 4), reaching 4.6 at 12 h of fermentation.
L. acidophilus is an obligatory homofermentative bacteriumthat produces
a single end product (lactic acid) from the glycolysis of carbohydrates
(EM pathway) (Rathore et al., 2012). High viable counts are
necessary to get the desired acid production and reduction in pH,
which affects organoleptic properties and shelf-life, and prevents
product contamination (Rathore et al., 2012). The cell populations
of L. acidophilus (LACA 4) increased rapidly within the first 8 h of fermentation
and remained stable at 7.9 log CFU/mL. After 24 h under
refrigerated conditions the viable cell counts were about
7.75 log CFU/mL (Fig. 1).
The growth of Lc. lactis (CCT 0360) over 24 h was slow and constant
reaching 8.25 log CFU/mL at 24 h. The slowgrowth reflected in the acidification
curve showing an equally slow acidification rate in peanut-soy
beverage, with a pH of 5.8 eventually reached after 24 h. Therefore, the
PSM provided appropriate growth and fermentation conditions for the
pure microbial cultures. L. acidophilus (LACA 4) and P. acidilactici
(UFLA BFFCX 27.1) presented populations above 8 log CFU/mL and
may preserve the low pH of the final beverage. The use of S. cerevisiae
(UFLA YFFBM 18.03) may give rise to a new class of products, where
the addition of yeast may serve as a source of protein and vitamin B
(Steinkraus, 1996). Thus, these strains were selected to be co-cultured
to obtain short fermentation periods and larger populations of the probiotic
bacteria.