Multi-step feeding systems for lactic acid production by simultaneous saccharification and fermentation of processed wood

Eucalyptus globulus wood samples were delignified in acetic acid media and swelled with NaOH solutions in a further stage. Solid residues from treatments were used as substrates for lactic acid production by Simultaneous Saccharification and Fermentation (SSF) in media containing Trichoderma reesei cellulases and Lactobacillus delbrueckii cells. The improvements in the overall process derived from adding fresh enzymes and/or substrate during the SSF process were assessed. In order to obtain comparative data on the efficiency of substrate utilization, enzymatic hydrolysis runs (in absence of microorganisms) were also carried out. Lactic acid concentrations in the range 48-62 g/l were obtained in SSF experiments. The solid residues after SSF (made up of microbial biomass and the non-hydrolyzed fraction of substrate) were characterized for measuring their potential as feed additives.