Improved high solid loading enzymatic hydrolysis of low-temperature aqueous ammonia soaked sugarcane bagasse using laccase-mediator system and high concentration ethanol production

High solids loading hydrolysis (HSLEH) of sugarcane bagasse (SCB) pretreated by low temperature aqueous ammonia soaking (AAS) was performed to obtain high concentrations of glucose and further fermentation to high concentration of ethanol. HSLEH was performed by fed batch addition of substrate and one-time enzyme feed at starting point. When the solids loading at 40% was tried in fed-batch hydrolysis, the observed concentrations of glucose and ethanol were 119 g/l and 58.4 g/l respectively. When laccase (200 U/g solids) with 1-HBT (25 mg/g solids) as a mediator was added to cellulase in HSLEH, the glucose and ethanol concentrations were further enhanced to 157 g/l and 72.4 g/l. The present glucan conversion of 74% in HSLEH was higher when compared with the reported values for biomass pretreated by high temperature steam explosion, acid and alkali pretreatments. The present ethanol concentration (72.4 g/l) was also higher than the reported levels of ethanol in the second-generation bioethanol production. As HSLEH of biomass by low temperature AAS has not been reported so far, the present results clearly demonstrates that LMS assisted HSLEH of biomass pretreated by low temperature AAS is promising for cellulosic ethanol production.