초록
l-Lactic acid (L-LA) is one of the microbial products with several applications and its production efficiency is so important. In the present study, we have been exploring application of low intensity ultrasound technology to improve the metabolic activity for l-lactic acid production by Lactobacillus casei in different mediums. L-LA, biomass production and substrate (protein) consumption were measured as parameters of fermentation yield. L-LA and protein contents were determined using the titratable acidity and the biuret method respectively. Spectrophotometry (OD<SUB>600nm</SUB>) was used for measuring cell growths. L-LA, biomass production and protein consumption considered as dependent variables, but the amplitude of waves (20%, 40% and 60%), waves duration (15, 30, 45s) and add of peptone (2, 6 and 10g/l) as independent variables. The results showed that L-LA, biomass production and substrate consumption significantly increased (@?25%). Optimum conditions for biomass production was amplitude of 60%, 15s exposure time and 10g/l peptone, while for acid lactic production and substrate consumption was 40%, 30s and 6g/l peptone, respectively. Flowcytometry analysis also showed that sonication led to increasing cell membrane permeability. This observation shows low intensity ultrasound as a potential parameter in the improvement of metabolic activity of L. casei.