Utilization of bamboo biomass as a biofuels feedstocks: Process optimization with yeast immobilization and the sequential fermentation of glucose and xylose

Abstract

Tropicalization of temperate climate zones due to global warming causes the destruction of ecosystems because it encourages the spread of invasive plant species such as bamboo. These species are usually removed from the affected areas to combat their spread. However, an efficient method to utilize these species has not yet been developed yet. Here, we investigated the potential of using invasive bamboo species as energy crops for biofuel production. Pretreatment of the bamboo with hydrogen peroxide–acetic acid (HPAC) and optimization of the enzymatic hydrolysis process with respect to the substrate concentrations, enzyme doses, and the synergistic effects of enzymes improved the productivity to increase the yield of glucose and xylose obtained from various bamboo types. Separate hydrolysis and fermentation (SHF) through calcium–alginate immobilized yeast greatly increased the cost competitiveness of producing bioethanol in that it successfully maintained the fermentation efficiency, even when reused for the fourth time. The sequential fermentation of glucose and xylose by Saccharomyces cerevisiae and Scheffersomyces stipitis, respectively, increased the bioethanol production by 13% over that of conventional fermentation using only glucose. Cost reduction achieved via immobilization of yeast and increased bioethanol productivity through sequential fermentation, as demonstrated here, further highlights the potential of bamboo as an energy crop.