Ball Milling Pretreatment of Corn Stover for Enhancing the Efficiency of Enzymatic Hydrolysis

Abstract

Ethanol can be produced from lignocellulosic biomass with the usage of ball milling pretreatment followed by enzymatic hydrolysis and fermentation. The sugar yields from lignocellulosic feed stocks are critical parameters for ethanol production process. The research results from this paper indicated that the yields of glucose and xylose were improved by adding any of the following dilute chemical reagents: H(2)SO(4), HCl, HNO(3), CH(3)COOH, HCOOH, H(3)PO(4), and NaOH, KOH, Ca(OH)(2), NH(3)·H(2)O in the ball milling pretreatment of corn stover. The optimal enzymatic hydrolysis efficiencies were obtained under the conditions of ball milling in the alkali medium that was due to delignification. The data also demonstrated that ball milling pretreatment was a robust process. From the microscope image of ball milling-pretreated corn stover, it could be observed that the particle size of material was decreased and the fiber structure was more loosely organized. Meanwhile, the results indicate that the treatment effect of wet milling is better than that of dry milling. The optimum parameters for the milling process were ball speed of 350 r/min, solid/liquid ratio of 1:10, raw material particle size with 0.5 mm, and number of balls of 20 (steel ball, Φ = 10 mm), grinding for 30 min. In comparison with water milling process, alkaline milling treatment could increase the enzymatic hydrolysis efficiency of corn stover by 110%; and through the digestion process with the combination of xylanase and cellulase mixture, the hydrolysis efficiency could increase by 160%.

Production of Biofuels from Cellulose of Woody Biomass

“…Various pretreatment processes of lignocellulosic feedstock [14] Physical pretreatment consists of mechanical disruption of lignocelluloses, which is an environmentally friendly process. This process increases the surface area of biomass and decreases the crystallinity of cellulose, but it does not cause an expensive mass loss [25]. Irradiation using gamma rays, electron rays and microwaves are other physical methods to beak the structure of lignocelluloses.…”

“…The oxidative biodegradation of lignin by white-rot fungi has been widely studied in the past [36]. The main advantages of biological pretreatment are low energy input, no chemical requirement, mild environmental conditions and environmentally friendly working manner [25]. However, the biological pretreatment processes usually need a long retention time and have a low yield.…”

“…pH, temperature, time, significantly affect the performance of enzyme hydrolysis. Furthermore, porosity and crystallinity and the lignin content of biomass seem to significantly influence the efficiency of this process [25].…”

“…However, acid hydrolysis may result in the production of undesirable by-products that should be eliminated prior to fermentation processes. These detoxification processes are generally costly and complicated [25,[40][41][42].…”

Understanding the mechanisms of cooperative physico-chemical treatment and mechanical disintegration of biomass as a route for enhancing enzyme saccharification

“…Such techniques are designed to bring about an increase in accessible surface area, which in turn leads to an enhancement in enzyme digestion rate and yield. Previous studies have shown that dry ball-milling of untreated biomass can be effective in this regard [14,15] although this may be a lengthy and energy-intensive operation [16,17]. Wet-state mechanical disintegration is more advantageous in that it avoids the energy expense of drying and can be integrated into a sequence of other wet processing steps, either as a pretreatment [18,19] or combined with simultaneous enzymatic treatment [20,21].…”