Effect of various pretreatment methods on sugar and ethanol production from cellulosic water hyacinth

Abstract

Effects of acid, alkali, ionic liquid (IL), and microwave-alkali pretreatments on cellulosic water hyacinth (WH) were investigated based on the total reducing sugars (TRS) and ethanol production. For the first time, IL pretreatment with (1-Ethyl-3-methylimidazolium acetate ([EMIM][Ac]) was used for WH, and the efficiency was compared with the other methods. Cellulase and Saccharomyces cerevisiae were fermented together for 72 h. Based on the results, all pretreatment methods effectively increased the sugar content as well as the ethanol yield. Untreated WH had 25 ± 1.5 mg/g of TRS, which was increased to 157 ± 8.2 mg/g, 95 ± 3.1 mg/g, 51 ± 4.2 mg/g, and 45 ± 2.6 mg/g via alkali, microwave-alkali, acid, and IL pretreatments, respectively. The highest TRS level of 402 mg/g was obtained in 24 h and 6.2 ± 0.4 g/L of ethanol in 48 h of fermentation with the alkali-treated WH. The ethanol production was followed by other treatment methods of WH in the order of microwave-alkali, acid, and IL. The results indicated that the ethanol production from WH was related to the type of pretreatment as well as the TRS production.

Changes in composition and structure of water hyacinth based on various pretreatment methods

“…The untreated WH consisted of 16.4% ± 0.35% cellulose, 32.7% ± 0.14% hemicellulose, and 5.7% ± 0.05% lignin, as reported in previous research (Rezania et al 2019). Narra et al (2017) reported 38.01% ± 1.26% cellulose, 24% ± 0.74% hemicellulose, and 9.50% ± 0.84% lignin in WH dry matter.…”

“…In this study, four types of pretreatments were performed: acid, alkali, IL, and microwave-alkali. The pretreatment specifications were like those in a previous study (Rezania et al 2019). The alkali pretreatment was performed at four different concentrations of NaOH (4%, 5%, 6%, and 7%) at 110 °C and a pH of 5.…”