Bioconversion of orange peels for ethanol production using Bacillus subtilis and Pseudomonas aeruginosa

Fruit processing industries produce large amount of waste material, which poses considerable disposal problems leading to pollution. The potentiality of Bacillus subtilis and Pseudomonas aeruginosa to produce ethanol from orange peels was investigated in the present study. Optimization of parameters to improve ethanol production was done. Maximum amounts of ethanol were produced using 8% orange peels. With the addition of 2% sucrose, ethanol production reached 67.20 g/l by B. subtilis whereas, in P. aeruginosa addition of lactose at a concentration of 2.5%, increased ethanol production till 55.20 g/l. B. subtilis produced maximum ethanol (75.20 g/l) when ammonium chloride was added to the medium at 4 g/l whereas, corn steep liquor at 5 g/l caused maximum ethanol production (69.50 g/l) by P. aeruginosa. The optimum environmental conditions that influence ethanol production in B. subtilis include inoculum concentration, pH, temperature and incubation time; 10%, pH: 7, 35°C for 72 h and in P. aeruginosa; 10%, pH: 8, 35°C for 72 h respectively. At these optimal conditions, the maximum ethanol production reached 92.25 and 82.70 g/l for B. subtilis and P. aeruginosa, respectively was recorded.