Concurrent production of sodium lignosulfonate and ethanol from bagasse spent liquor.

This study was done with the aim of lignosulfonate and ethanol production from different spent liquors of bagasse pulping process. For this purpose, alkali lignin from bagasse alkali liquor was separated and was sulfomethylated to produce soda lignosulfonate (SLig). Furthermore, raw bagasse was directly treated with sodium sulfite in acidic and neutral conditions to produce BLig and NLig bagasse lignosulfonate, respectively. In addition, the pentoses and hexoses impurities in lignosulfonates were fermented to ethanol using Candida guilliermondii. Results showed that the molecular weight of NLig lignosulfonate was considerably high comparing to the SLig and BLig lignosulfonates. A high level of thermal resistance was found in case of SLig regarding to the other samples at 500 °C. Fermentation of the spent liquors with Candida guilliermondii led to a maximum ethanol yield of 7.0, 1.0 and 5.1 g L-1 in NLig, SLig and BLig, respectively.