Use of Spectroscopic and Imaging Techniques to Evaluate Pretreated Sugarcane Bagasse as a Substrate for Cellulase Production Under Solid-State Fermentation

Abstract

The enzymatic cocktail of cellulases is one of the most costly inputs affecting the economic viability of the biochemical route for biomass conversion into biofuels and other chemicals. Here, the influence of liquid hot water, dilute acid, alkali, and combined acid/alkali pretreatments on sugarcane bagasse (SCB) used for cellulase production was investigated by means of spectroscopic and imaging techniques. Chemical composition and structural characteristics, such as crystallinity (determined by X-ray diffraction), functional groups (Fourier transform infrared spectroscopy), and microstructure (scanning electron microscopy), were used to correlate SCB pretreatments with enzymatic biosynthesis by a strain of the filamentous fungus Aspergillus niger under solid-state fermentation. The combined acid/alkali pretreatment resulted in a SCB with higher cellulose content (86.7%). However, the high crystallinity (74%) of the resulting biomass was detrimental to microbial uptake and enzyme production. SCB pretreated with liquid hot water yielded the highest filter paper cellulase (FPase), carboxymethyl cellulase (CMCase), and xylanase activities (0.4, 14.9, and 26.1 U g(-1), respectively). The results showed that a suitable pretreatment for SCB to be used as a substrate for cellulase production should avoid severe conditions in order to preserve amorphous cellulose and to enhance the physical properties that assist microbial access.

Effects of Pretreatment of Single and Mixed Lignocellulosic Substrates on Production of Endoglucanase by Bacillus aerius S5.2

“…The high CrI value of the OPF was due to the severity of the pretreatment on this substrate as compared with EFB and RH. Higher CrI values are consistent with decreased abundance of amorphous portions of biomass (amorphous cellulose, hemicellulose, and lignin) following their removal during pretreatment (Rodriguez-Zuniga et al 2014). This is supported by the chemical composition of the substrates (Table 2), which showed that samples with higher CrI had lower amorphous components (EFB-37.18%, OPF-31.36%, and RH-39.66%) viz.…”

On-Site Production of Enzymatic Cocktails Using a Non-conventional Fermentation Method with Agro-Industrial Residues as Renewable Feedstocks

“…Widespread production of 2G ethanol is therefore expected in the near future. In recent decades, lignocellulosic materials such as plants and agricultural residues have been employed as low-cost feedstocks in ethanol production processes, both as inducer substrates for enzyme production [3][4][5] and as feedstocks for bioconversion into fermentable sugars [6][7][8][9].…”

“…However, the development of bioprocesses using complex substrates such as agricultural residues is hampered by the fact that the composition and structure of lignocellulosic materials vary significantly from one plant to another, and even among plants of the same species. Different ratios of cellulose, hemicellulose, and lignin in the plant cell wall, as well as the degree of crystallinity of the cellulose, surface area, and porosity, among other factors, can affect the fungal assimilation of lignocellulose and consequently influence the expression of hydrolytic enzymes [3,22].…”

Fermentation Optimization and Unstructured Kinetic Model for Cellulase Production by Rhizopus stolonifer var. reflexus TP-02 on Agriculture By-Products

“…Given the special transcription regulation system existing in fungi, the high-production of extracellular fungal cellulase complex often needs inducers such as cellulosic or lignocellulosic substrates [22]. As a carbon source or inducer, the pretreated rice/ wheat straw has been approved to be an efficient substrate for cellulase production [20,21].…”

“…Among the optimal cellulase-producing approaches, one effective method to reduce enzyme production cost is to replace pure cellulose and other sugars with relatively cheaper substrates [17,18]. The agricultural by-products and wastes, which are abundant and disposable but rich in lignocellulosic substrate, such as wheat/ rice bran [19,20], wheat/rice straw [20,21], sugar cane bagasse [22], and groundnut husk [23], have been tested successfully in the production of cellulases by fungi. Moreover, these less expensive lignocellulosic raw materials can support microbial growth while inducing cellulase expression.…”