Simultaneous Saccharification and Fermentation of Bagasse Sulfite Pulp to Lactic Acid by Bacillus coagulans CC17

Lignocellulosic biomass is an economical and renewable feedstock for microbial production of bulk chemicals such as lactic acid. In many cases, simultaneous saccharification and fermentation (SSF) can achieve lower cost and higher productivity than the classical double step fermentation. Thus, in the present study, bagasse sulfite pulp was directly employed to produce lactic acid by SSF, using thermophilic Bacillus coagulans strain CC17. The effects of various factors, including CaCO3 addition time and the initial buffered pH, on lactate production were investigated. It was found that Bacillus coagulans strain CC17 could perform well at conditions that are also optimal for fungal cellulase. The addition of CaCO3 as the buffering reagent is critical for the production of lactic acid and maintaining pH. Maximum production of lactic acid was obtained by adding CaCO3 after 3 h fermentation. When pH 7 was used as the initial pH, strain CC17 produced about 20.68 g/L lactic acid from 20 g/L cellulose content of BSP with 15 FPU of Cellulast 1.5L/g cellulose and 15 CBU of Novozyme 188 /g cellulose. The results showed that this strain has potential to be used for direct lactic acid fermentation from lignocellulosic biomass via SSF.