Medium optimization of lactobacillus casei cultivation for cell mass production in semi-industrial scale bioreactor

Abstract

Good health is an essential key for a happy life. Probiotics have numerous health benefits, hence it has gained a big global market for commercialization. The main challenge in the probiotic commercialization is the bioprocessing limitation to produce high cell mass, especially when involving the cultivation of lactic acid bacteria (LAB) which produces lactic acid as its byproduct. Low cell growth and lactic acid accumulation which leads to cell death are the challenges in large scale bioreactor cultivation. In this study, cultivation media of Lactobacillus casei strain WICC-B26 was optimized in shake flask through one factor at a time (OFAT) method and response surface methodology (RSM). The OFAT optimized medium consists of 50 g.L-1 lactose, 60 g.L-1 soybean meal, 6 g.L-1 yeast extract and 0.4 g. L-1 MgSO4. The OFAT optimized medium produced 6.9 g. L-1 cell mass of Lactobacillus casei, which was higher than the RSM optimized media (6.52 g. L-1). Hence, the OFAT medium was selected for the fermentation to choose the best pH condition in 16 L stirred tank bioreactor. The uncontrolled pH condition produced higher cell mass (42.68%) compared to the pH controlled condition pH 6.5. After selecting the pH condition, the effect of different aeration condition was studied in the 16 L stirred tank bioreactor. The maximum biomass produced by the carbon dioxide sparging (0.2 vvm CO2 gas) and cultivation with no aeration were 6.16 and 5.9 g. L-1 respectively. The results show that all the aeration conditions, no aeration, 0.2 vvm CO2 sparging and microaerophilic condition (0.2 vvm air) produced similar outcome in terms of the biomass produced, which means Lactobacillus casei is able to grow in all 3 aeration conditions applied in this research. The outcome of this research is expected to serve as a basis for further research with complete anaerobic and fed-batch cultivation to improvise the production of Lactobacillus casei biomass in the future.