Lactic Acid Production by Clostridium acetobutylicum and Clostridium beijerinckii Under Anaerobic Conditions Using a Complex Substrate

Abstract

SUMMARY/ ABSTRACTHigh societies consumption, elevated residues generation and environmental awareness strengthen alternatives solutions for bioprocess residues. This study investigated the production of volatile acids from a complex substrate, which intends to be replaceable in the future by vinasse of sugar cane, in anaerobic reactors operated in triplicates at 35 {degrees}C. Two different inoculum were studied: Clostridium acetobutylicum ATCC 824 and Clostridium beijerinckii ATCC 25752. The nutrient medium had as carbon source a complex substrate containing sucrose without addition of vitamins, buffer solution and micronutrients. The experiment was conducted in the variation of F/M-ratio (food-to-microorganisms) by increasing substrate concentration. The concentration of sucrose in the complex substrate were 5.2 g{middle dot}L-1 (conditions of 10,000 mg O2{middle dot} L-1 in terms of COD) and 10.5 g{middle dot} L-1 (conditions of 20,000 mg O2{middle dot}L-1 in terms of COD), keeping the initial concentration of inoculum in 500 mg SVT{middle dot}L-1. Cultures C. acetobutylicum and C. beijerinckii resulted in high lactic acid production. Concentrations of COD of 10,000 mg O2{middle dot} L-1 produced optimum lactic acid of 3,331 mg{middle dot}L-1 and 5,709 mg{middle dot}L-1 with respectively C. acetobutylicum and C. beijerinckii. Moreover, cultures C. acetobutylicum and C. beijerinckii with 20,000 mg O2{middle dot} L-1 concentrations in terms of COD produced optimum lactic acid of 6,417 mg{middle dot} L-1 and 7.136 mg{middle dot}L-1 respectively. There was repeatability in the reactors when considering level of significance of 0.05, independent of the concentration and inoculum used.