Bioprocess Optimization for High Biomass Production of Bacillus Firmus

Bacillus firmus are natural occurring bacteria in the soil environment. B. firmus are economically important in agricultural sector whereby the application as biocontrol agent against disease caused by nematodes. B. firmus categories as gram positive bacteria rod shape. Research conducted proved that Bacillus sp. is able to secrete extracellular enzyme such as protease in which act as a nematicidal agent to control the population of parasite nematodes. The life cycle of B. firmus divided into two phase which consists of growth of vegetative cells and endospores formation. Production of high cell mass for different kind of microorganisms, requires extensive study by developing a suitable medium and cultivation strategy. This study will focusing on the development of production medium started with screening of different production media to select the best medium which supports the higher cell growth. The best medium consist of glucose, 20.0 g L^-1; peptone from casein 5.0 g L^-1; yeast extract 2.0 g L^-1, potassium dihydrogen phosphate, 5.0 g L^-1; and magnesium sulphate heptahydrate, 2.0 g L^-1 gave highest cell mass of 6.27 g L^-1 in shake flask culture. Hence, the medium optimization was carried out by using two approaches: One Factor at Time (OFAT) and statistical optimization. The produced biomass by using un-optimized and optimized medium both yielded 6.82 g L^-1 and 10.22 g L^-1, respectively. As step for bioprocess industrialization, cultivations were carried out using batch mode in 16-L bioreactor under controlled and uncontrolled pH conditions. The maximal biomass produced was 11.91 g L^-1 in uncontrolled pH culture. Furthermore, cells were cultivated in fed-batch culture using different feeding strategies. Feeding of complete medium using constant rate has increased the biomass production up to 14.89 g L^-1. Furthermore, feeding of complete medium components by increasing the feeding rate at 1.027 g L^-1 h^-1 for every 10 hours under uncontrolled pH cultivation of B. firmus, the cell mass was increased up to 28.07 % with the maximal cell mass achieved was 19.16 g L^-1.