Acid hydrolysis of corn cob for the production of second generation ethanol by saccharomyces cerevisiae atcc 26602

Corn is one of the most produced crops in Brazil, during its processing it generates rejects such as cobs, stalk, leafs and straw that can be used as biomass for the production of second generation bioethanol (2G). However, for the reutilization of this substrate it is necessary the application of a treatment for the removal of lignin, fragmentation of hemicellulose and cellulose into corresponding sugars to be converted into ethanol by microorganisms. Therefore, the purpose of this research was to perform acid hydrolysis of corn cob and utilizing the hydrolyzate as a culture medium for the production of ethanol 2G by yeast Saccharomyces cerevisiae ATCC 26602. Initially it was evaluated the effect of various concentrations of sulfuric acid and various times of exposure to the acid solution to determine the efficiency of the hydrolysis. Next it was carried out the removal of phenolic compounds generated during the hydrolysis (detoxification). Following that, it was analyzed the effect of various agitation speeds in the production of ethanol by the yeast in question. The hydrolysis had more efficiency when performed with 2.5% of sulfuric acid and exposure time of 30 min. The hydrolyzate detoxification resulted in the lowering of phenolic compounds that act as inhibitors of the fermentation. The yeast was capable of utilizing the raw hydrolyzate (RH) and detoxified raw hydrolyzate (DRH) for cellular growth and biosynthesis of ethanol under agitated environment. Maximum ethanol production (8.11 g.L-1) was obtained in 100 rpm agitation tests after 36 hours of fermentation. The results imply that detoxified corncob hydrolyzate culture medium could be an efficient alternative for the production of second generation ethanol by the yeast S. cerevisiae ATCC 26602. Furthermore, the yeast was able to grow and produce ethanol on the raw hydrolyzate, which removes one stage in the production of 2G ethanol.