GROWTH ENHANCEMENT OF BIFIDOBACTERIUM-LACTIS BO AND LACTOBACILLUS-ACIDOPHILUS KI BY MILK HYDROLYZATES

The determination of the best conditions of preparation of a (tentativ ely) probiotic starter culture that might be suitable for cheese makin g composed solely of Bifidobacterium lactis Bo and Lactobacillus acido philus Ki is critical if a consistently reliable acid production is to be achieved, especially because bifidobacteria have stringent require ments for growth. Therefore, we determined whether B. lactis Bo and L. acidophilus Ki required or benefitted from the addition of milk hydro lyzates (brought about by proteinase or neutrase as the nitrogen sourc e). The growth acid acid production of B. Lactis in milk were affected by the addition of proteinase-mediated hydrolyzate and, to a lesser e xtent, by neutrase-mediated hydrolyzate; a higher degree of hydrolysis of either hydrolyzate resulted in greater biomass increase and greate r acid production. This result suggests that the poor growth of bifido bacteria in milk is due partially to the lack of small peptides and fr ee amino acids. The rates of growth and acidification by B. lactis wer e enhanced when cocultured with L. acidophilus (1:1 inoculum ratio). C onversely, the growth rates and acid production of L. acidophilus were not positively affected by the addition of either milk hydrolyzate. A lthough L. acidophilus grew slowly, its proteolytic system was apparen tly able to generate its own nitrogen source. Nevertheless, coculture with B. lactis (1:1 inoculum ratio) led to enhanced rates of growth an d acidification when compared with that of the single strain, suggesti ng some degree of symbiosis between the strains.