Hydrothermal and wet disk milling pretreatment for high conversion of biosugars from oil palm mesocarp fiber

Abstract

Eco-friendly pretreatment methods for lignocellulosic biomass are being developed as alternatives to chemical based methods. Superheated steam (SHS), hot compressed water (HCW) and wet disk milling (WDM) were used individually and with combination to partially remove hemicellulose and alter the lignin composition of recalcitrant structure of oil palm mesocarp fiber (OPMF). The efficiency of the pretreatment methods was evaluated based on the chemical compositions altered, SEM analysis, power consumption and degree of enzymatic digestibility. Hemicellulose removal (94.8%) was more pronounced under HCW compared to SHS, due to maximal contact of water and production of acetic acid which enhanced further degradation of hemicellulose. Subsequent treatment with WDM resulted in defibrillation of OPMF and expansion of the specific surface area thus increasing the conversion of cellulose to glucose. The highest glucose yield was 98.1% (g/g-substrate) when pretreated with HCW (200 °C, 20 min) and WDM which only consumed 9.6 MJ/kg of OPMF.

Influence of High-Pressure Steam Pretreatment on the Structure of Rice Husk and Enzymatic Saccharification in a Two-Step System

“…In fact, when the commercial cellulase was hydrolysed at 60 °C, the reducing sugar production and saccharification degree decreased as the hydrolysis time increased to 72 h. This was because most fungi are mesophilic in nature, thus might not contain enzymes that are adapted to thermophilic environments. Many studies have reported on the enzymatic hydrolysis of commercial cellulase from fungi at 50 °C (Hsu et al 2010;Zakaria et al 2015b;Wood et al 2016). After comparing the influence of time for hydrolysis of the B. licheniformis 2D55 cellulase at 50 and 60 °C, the results of this analysis suggested that conducting hydrolysis with B. licheniformis 2D55 cellulase at 60 °C can produce a faster rate of reducing sugar production and saccharification than that at 50 °C.…”

A comprehensive review on pre-treatment strategy for lignocellulosic food industry waste: Challenges and opportunities

“…The enzymatic degradability of the substrate was improved by this process. Zakaria et al (2015) used wet disk milling as a secondary pretreatment step to extract sugars from recalcitrant oil palm mesocarp fibre. They found that wet disk milling increased the surface area accessible for the conversion of cellulose to glucose.…”

Combined pretreatment with hot compressed water and wet disk milling opened up oil palm biomass structure resulting in enhanced enzymatic digestibility

“…The samples were prepared as discussed earlier (Zakaria et al, 2014a) prior to component analysis. Hot compressed water (HCW) pretreatment was performed using a 1 L stainless steel autoclave (Nitto Koatsu Co., Tsukuba, Japan) (Zakaria et al, 2015b). The oil palm biomass was pretreated at temperature ranges from 150 to 190°C for 10 and 240 min, respectively.…”

“…Superheated steam (SHS) treatment was tested on oil palm mesocarp fiber (OPMF) and the glucose conversion yield was not pronounced in comparison to hot compressed water (HCW) due to minimal contact of water that reacts as catalyst in the hydrolysis of hemicellulose component. Combination of pretreatment using HCW (180°C for 20 min) and WDM were the best method to recover the highest xylose (90%) and glucose (86%), and was preferred for pretreatment of OPMF (Zakaria et al, 2015b).…”