Inoculum variation study of Lactobacillus paracasei and Bifidobacterium longum on soy solid state fermentation

RODRÍGUEZ DE OLMOS, A; GARRO, MS

San Miguel de Tucumán

Simposio; IV Simposio Internacional de Bacterias Lácticas; 2013

Centro de Referencia para Lactobacilos (CERELA-CONICET)

Solid state fermentation (SSF) is a very interesting technological alternative to obtain new products due to it uses waste and cheap raw material like substrate. In this sense soy is a great substrate to use for its high nutritional value and low cost. In previous studies the behavior of Bifidobacterium (B.) longum CRL 849 and Lactobacillus (L.) paracasei subsp paracasei CRL 207 on soy SSF with different moisture content (50, 55, 65, 75, 80 %) and several temperatures (31, 33, 37, 41, 43 ºC) were analyzed. These assays were performed using 4% inoculum. These results demonstrated that both strains were able to develop on SSF proposed and some parameters of fermentative process were optimized. The conditions selected were: moisture 65% and 37ºC. The aim of this study was to analyze different inoculum concentrations on the behavior of both strains under previously optimized conditions of soy SSF. Pastes were made from commercial soy flour and distillated water to obtain 65% moisture; they were sterilized and inoculated with 1, 2 and 4% cultures of each strain. These were incubated at 37ºC for 24 h in adequate conditions for each strain and samples at different times (0, 4, 8, 12, 16, 24 h) were taken. The growth, through the measurement of pH and plate counts, proteolytic activity and beta-glucosidase activity were analyzed. At the end of fermentation, CRL 849 population reached around 9 log CFU g-1 for the three assayed inoculum and pH values decreased c.a. 1,55 times respect to the control, nevertheless the acidification rate was lower for 1% inoculum. The behavior was similar for the three conditions assayed respect to amino acids intake, soluble protein concentration decrease and beta-glucosidase activity enhancement compared with non-inoculated control. On the other hand, population of CRL 207 reached around 9.6 log CFU g-1 for the three inoculum, however pH values decreased slightly in all cases. Increase of amino acids amount and evidence of beta-glucosidase activity was observed without significant differences between inoculum concentrations. Taken together, obtained results show a different behavior for each strain. In addition, we can conclude that it is not necessary to work with 4% inoculum because with lower initial bacterial amounts is possible to obtain results with significant technological impact.