GROWTH OF BACILLUS SUBTILIS AND PRODUCTION OF ACETIC ACID WITH ROTTEN POTATO: USED AS SUBSTRATE

The Bacillus subtilis is anaerobic gram-positive, dominant and non-pathogenic bacterial workhorses in industrial fermentations. In present work, B. subtilis LC4 cultured on a number of combinations of TY-medium with peels and peeled-off rotten potatoes to investigate its growth and level of secondary metabolites production including acetic acid. Cell culture was harvested after 42 and 62 h and maximum growth rate was observed in LB₅ (peeled off potato extract) and LBo (TY-medium) cultures, while culture OD600 was low at 62h of all. It might be reduced with the shortage of nutrients in the medium that lead to killing of cells. Reducing sugars and total proteins were observed higher (p≤0.05) but reversed in both harvests to the decreasing rate of cell growth or multiplication rate of all cultures. Similar trend in production of acetic acid was also noted (p≤0.05) in all cultures. Increasing level of reducing sugars concentration among the culture indicates the cells are growing under nutritional stress. Meanwhile production of acetic acid along the higher concentrations of reducing sugars could be involved to initiate signals for sporogenesis in Bacillus subtilis cells. It could be a best adjustment of Bacillus cells for their survival in nutrient medium at stationary or decline growth phase. Both mixture of peels and starch extracts of rotten potato are recommended as the best productive and cheapest substrate for growth of Bacillus subtilis as well as may be recommended for microbial based extracellular proteins and acetic acid production.