Enterococcus sp. has been used as starters in food fermentation due to their probiotic and antimicrobial properties in food biopreservation. The antimicrobial properties were mainly contributed by the bacteriocin called enterocin. Hence, the availability of a cost-effective pilot-scale cultivation conditions is a necessity for the production of probiotic bacteria. This study aims to investigate optimization of medium composition using sugarcane molasses as a carbon source using response surface methodology and the potential use of fed-batch cultivation for improvement of the cell viability of Enterococcus faecium CW3801 for the use as a probiotic starter culture. Two feeding strategies (ramp and constant) were applied in fed-batch cultivation for enhancement of the production of E. faecium in a 2-L stirred tank bioreactor using the optimized medium and scaled up to a 15-L bioreactor. Optimized fermentation medium which comprised of 10% (v/v) of molasses and 10 g/L of yeast extract at pH 7 yielded maximum cell viability of 29.4 × 1011 CFU/mL with 3900 AU/mL of bacteriocin-like inhibitory substances (BLIS) activity. In the fed-batch, the cell viability (8.4 × 1013) and dry cell weight (6.34 g/L) reached the highest in optimized medium when the ramp (stepwise) feeding was applied. In scaling up to 15-L bioreactor, the growth of E. faecium was achieved at 2.3 × 1013 CFU/mL with the dry cell weight of 5.28 g/L under the same condition. The BLIS in 15-L bioreactor was 6% higher than the 2-L bioreactor. This study demonstrated that molasses and yeast extract are good feedstock for the growth of E. faecium. The E. faecium, a non-vancomycin resistant enterococcus (VRE) was successfully produced by a fed-batch cultivation approach and scaled up to a 15-L bioreactor using a ramp feeding strategy. Results from this study revealed that the fed-batch cultivation using molasses-based medium has industrial potential for the production of probiotics.
Keywords: Bioreactor; E. faecium; fed-batch; molasses; optimization.