Influence of different chemical pretreatments of elephant grass (Pennisetum purpureum, Schum.) used as a substrate for cellulase and xylanase production in submerged cultivation

Abstract

This study evaluated the potential use of elephant grass biomass, a highly productive species, for cellulase and xylanase production by the cellulolytic mutant Penicillium echinulatum 9A02S1 in submerged cultivation, using untreated biomass, biomass pretreated with different concentrations of NaOH, H2SO4 or NH4OH, or biomass pretreated with H2O at 121 °C. For filter paper activity, all cultivation carried out with pretreated elephant grass under the evaluated conditions showed superior activity when compared with the control (untreated elephant grass). The activities of endoglucanases and β-glucosidases were higher in the cultivation prepared from pretreated samples than the control made with cellulose (Celuflok(®)). Without pretreatment, elephant grass can be used for xylanase production, enabling similar activities to those obtained in the cultivation with cellulose, reducing the enzyme production cost. These results indicate that the pretreatment of elephant grass, especially when pretreated with H2SO4, may be used as a partial or total replacement for cellulose to cellulase production, and untreated elephant grass may be used for xylanase production.

Bioethanol Production From Lignocellulosic Biomass by Environment-Friendly Pretreatment Methods: A Review

“…These pretreatment methods decrease the cellulose crystallinity and the degree of polymerization as well as increase the specific surface area (Sanchez and Cardona, 2008). Menegol et al (2016) also revealed that physical pretreatment leads to higher ethanol production after delignification of elephant grass. However, studies demonstrated that more reduction of biomass particles i.e.…”

Enhanced Enzymatic Hydrolysis of Pennisetum alopecuroides by Dilute Acid, Alkaline and Ferric Chloride Pretreatments

“…The recalcitrant structure of lignocellulosic biomass is the main constraint of its bioconversion [13,14,15,16,17,18]. Varied pretreatment strategies such as chemical methods (e.g., acid, bases, salts and solvents), physico-chemical processes (e.g., steam explosion, liquid hot water (LHW) and ammonia fiber expansion (AFEX) and biological methods have been developed in attempts to remove hemicellulose and/or lignin from lignocellulosic wastes and reduce the crystallinity of cellulose [13,19,20,21,22,23,24]. It is widely accepted that efficient pretreatment should avoid the use of expensive chemicals, improve fiber reactivity and maximize the recovery/formation of fermentable sugars, avoid formation of enzyme inhibitory byproducts, preserve cellulose and hemicellulose fractions that are easily accessible to hydrolysis enzymes and minimize energy requirements [11,12,13,14].…”

“…On the other hand, corrosion problems and sugar degradation are less severe in alkaline processes than in acid pretreatment. Alkaline pretreatment is also effective in delignifying the biomass [7,20,22,24]. A mild alkali concentration (<4% w/w ) favors enzymatic hydrolysis especially for low-lignin materials [13,14].…”

“…Operating at milder temperature conditions (120 °C vs 160~260 °C in steam explosion and LHW pretreatments) in the current study means that dilute acid pretreatment (DAP), dilute alkaline pretreatment (DALP) and ferric chloride pretreatment (FCP) reduce energy consumption and the formation of enzyme inhibitory byproducts [11]. Up to date, DAP, DALP and FCP have been used on a wide range of low-lignin biomasses ranging from wood (cedar, pine, hemlock) to agricultural residues (corn stover, wheat and barley straw, switchgrass, Miscanthus ) [18,19,20,21,22,23,24]. To our best knowledge, the effects of these methods on the biodigestibility of P. alopecuroides has not been systematically studied to identify the ideal pretreatment process or to evaluate the potential of P. alopecuroides biomass in the bioconversion industry.…”

One-Step or Two-Step Acid/Alkaline Pretreatments to Improve Enzymatic Hydrolysis and Sugar Recovery from Arundo Donax L.

“…The bioconversion process is still constrained due to the recalcitrance of these energy crops. Different pretreatment strategies such as pretreatments using acid, alkaline or hot water, explosion pretreatments with steam or ammonia, and biological pretreatment have been reported for reducing the recalcitrance of lignocellulosic biomass wastes, and hence, enhancing the digestibility of these biomass wastes [12][13][14][15][16][17][18]. Chemical pretreatment has been extensively investigated, from lab-scale studies to large-scale ethanol fermentation applications, especially those using low lignin biomass (e.g., agricultural wastes) as substrates [15][16][17][18].…”