Developing an optimum pretreatment condition to enhance glucose recovery assessed the potential of Chloris barbata, which is a common invasive weed in Thailand, as a feedstock for bioethanol production. Chloris barbata was exposed to autoclave-assisted alkaline pretreatment by using different sodium hydroxide (NaOH) concentrations (1% to 4%) and heat intensities (110 °C to 130 °C) that were dissipated from autoclaving. The optimum condition for pretreatment was determined to be 2% NaOH at 110 °C for 60 min. At this condition, maximum hydrolysis efficiency (90.0%) and glucose recovery (30.7%), as compared to those of raw C. barbata (15.15% and 6.20%, respectively), were observed. Evaluation of glucose production from 1000 g of C. barbata based on material balance analysis revealed an estimated yield of 304 g after pretreatment at the optimum condition when compared to that of raw C. barbata (61 g), an increase of five-fold. Structural analysis by the scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the disruption of the intact structure of C. barbata and an increase in the cellulose crystallinity index (CrI), respectively. The results from this study demonstrate the efficiency of using C. barbata as a potential feedstock for bioethanol production.

The potential of durian (Durio zibethinus Murr.) peel as feedstock for the production of fermentable sugars was evaluated. Durian peel biomass from two cultivars, monthong (Durio zibethinus Murr. cv. Monthong) and chanee (Durio zibethinus Murr. cv. Chanee), were pretreated with different concentrations (70%, 75%, 80%, and 85%) of phosphoric acid (H₃PO₄) at a moderate temperature of 60 °C for 60 min. The H₃PO₄-pretreated durian peel biomass was then subjected to enzymatic hydrolysis. Significantly higher glucan (44.74 ± 0.21%) content was observed in the monthong peel compared to the chanee peel (42.06 ± 0.28%). Phosphoric acid pretreatment caused the significant solubilization of the xylan and acid soluble lignin (ASL) contents. This enhanced the enzymatic hydrolysis process causing a significant increase in the hydrolysis efficiency and glucose concentration. The highest hydrolysis efficiency and glucose concentration were obtained after 72 h from the 75% H₃PO₄-pretreated peel biomass for both the monthong (90.33 ± 0.42% and 9.55 ± 0.11 g/L, respectively) and chanee (90.06 ± 0.40% and 8.56 ± 0.13 g/L, respectively) peels. Biomass to glucose recovery for monthong and chanee were improved by approximately 7- and 6-fold, respectively. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed destruction of the peel biomass structure and changes in the cellulose crystallinity index (CrIs).

Durian (Durio zibethinus Murr.) peel, as agricultural waste, is a potential under-utilized lignocellulosic biomass that is sufficiently available in Thailand. In this study, durian peel from monthong (D. zibethinus Murr. cv. Monthong) and chanee (D.zibethinus Murr. cv. Chanee) were subjected to pretreatment with sodium hydroxide (NaOH) under autoclaving conditions to improve glucose recovery. The effect of NaOH concentration (1%, 2%, 3%, and 4%) and autoclave temperature (110 °C, 120 °C, and 130 °C) was investigated based on the amount of glucose recovered. The optimal NaOH concentration and autoclave temperature were determined to be 2% and 110 °C, respectively, under which maximum glucose (36% and 35% in monthong and chanee peels, respectively) was recovered. Glucose recovery was improved by about 6-fold at the optimal pretreatment condition for both pretreated monthong and chanee when compared to the untreated durian peels. Scanning electron microscopy (SEM) showed great changes to the surface morphology of pretreated durian peel from the two cultivars. X-ray diffraction (XRD) analysis also revealed a rise in cellulose crystallinity index (CrIs) after pretreatment. A combination of mild NaOH concentration and autoclaving is a very effective pretreatment technique for maximum glucose recovery from durian peel.