Impact of pretreatment methods on production of bioethanol and nanocrystalline cellulose

Abstract

Cellulose, the most abundant terrestrial biopolymer, has immense potential for a range of applications, such as textiles, biomedical applications, and sustainable building components. Due to the recalcitrant nature of lignocellulosic materials, various alkaline and acid pretreatment methods have been developed to recover mono sugars for fermentation. Simultaneous production of bioethanol and nanocrystalline cellulose (NCC) from pretreated Formosan alder biomass was conducted in two stages. Formosan alder biomass was treated using unbleached kraft (UEK), acid steam explosion (SEP), and bleached acid steam explosion (BSEP) and hydrolyzed using cellulase. Filter paper (FP) and alpha-cellulose were used as positive controls. Bioethanol fermentation using E. coli Ko11 was conducted. Residual biomass was further recovered to produce NCC. After 96 h enzyme hydrolysis, the highest sugar yields were 383.4 and 329.84 mg glucose/g biomass for the FP and UEK samples. The highest bioethanol fermentation yields were 4.18 and 3.62 g bioethanol/g biomass for FP and UEK samples. During enzyme hydrolysis of the biomass, crystallinity increased. NCC yields were 613.93 nm (68%) and 1583 nm (73%) for the FP and UEK samples. The negative impact of lignin content was reflected in the particle length of the final NCC. Further lignin removal is required for optimal NCC production. This study showed that Formosan alder biomass could be used to produce both bioethanol and NCC.