Use of an (Hemi) Cellulolytic Enzymatic Extract Produced by Aspergilli Species Consortium in the Saccharification of Biomass Sorghum

Transcriptome-wide analysis of a superior xylan degrading isolate Penicillium oxalicum 5-18 revealed active lignocellulosic degrading genes

Lignocellulose biomass raw materials have a high value in energy conversion. Recently, there has been growing interest in using microorganisms to secret a series of enzymes for converting low-cost biomass into high-value products such as biofuels. We previously isolated a strain of Penicillium oxalicun 5-18 with promising lignocellulose-degrading capability. However, the mechanisms of lignocellulosic degradation of this fungus on various substrates are still unclear. In this study, we performed transcriptome-wide profiling and comparative analysis of strain 5-18 cultivated in liquid media with glucose (Glu), xylan (Xyl) or wheat bran (WB) as sole carbon source. In comparison to Glu culture, the number of differentially expressed genes (DEGs) induced by WB and Xyl was 4134 and 1484, respectively, with 1176 and 868 genes upregulated. Identified DEGs were enriched in many of the same pathways in both comparison groups (WB vs. Glu and Xly vs. Glu). Specially, 118 and 82 CAZyme coding genes were highly upregulated in WB and Xyl cultures, respectively. Some specific pathways including (Hemi)cellulose metabolic processes were enriched in both comparison groups. The high upregulation of these genes also confirmed the ability of strain 5-18 to degrade lignocellulose. Co-expression and co-upregulated of genes encoding CE and AA CAZy families, as well as other (hemi)cellulase revealed a complex degradation strategy in this strain. Our findings provide new insights into critical genes, key pathways and enzyme arsenal involved in the biomass degradation of P. oxalicum 5-18.

Bioprocessing of oilseed cakes by fungi consortia: Impact of enzymes produced on antioxidants release

Oilseed cakes (OC) present high potential as feedstock for the biobased industry. Biotechnological processes allow OC valorization by the production of diverse value-added products and simultaneously altering OC structure, improving their nutritional value, and boosting OC utilization in animal feed. This work explored the use of fungi consortium of two different species as a bioprocessing approach to improve the nutritional quality of OC, obtain enzymes and antioxidants by solid-state fermentation (SSF) of sunflower cake (SFC) and rapeseed cake (RSC). Rhyzopus oryzae and Aspergillus ibericus consortium led to the highest production of cellulase (135 U/g) and β-glucosidase (265 U/g) while maximum protease (228 U/g) was obtained with A. niger and R. oryzae consortium. Maximum xylanase production (886 U/g) was observed in SSF of RSC resulting in high hemicellulose reduction. The synergistic action of lignocellulosic enzymes resulted in extracts with increased antioxidant potential with possible application as food additives against oxidative stress.

Production, concentration and partial characterization of an enzymatic extract produced by an Aspergillus niger mutant in solid state fermentation

An enzymatic extract from Aspergillus niger 3T5B8 was produced by Solid State Fermentation (SSF) in aerated columns, using wheat bran as substrate. A combination of extracts produced using three different process conditions varying temperature, pH and aeration formed the final extract (Mixture). The Mixture was concentrated by an ultrafiltration process that partially purified and provided an efficient recovery of the enzymatic activities of xylanase (88.89%), polygalacturonase (89.3%), β-glucosidase (93.15%), protease (98.68%) and carboxymethylcellulase (CMCase) (98.93%). SDS-PAGE analysis showed 15 visible protein bands in the crude and concentrated Mixture with molecular weights ranging from 15.1 to 104.6 kDa. Thin layer chromatography confirmed the effective action of β-glucosidase and xylanase hydrolysis activities over cellobiose and xylan, respectively. A central composite design (CCD) with two variables and four replicates at the center points was used to determine the optimal temperature and pH for CMCase and β-glucosidase. The optimal temperature was 78.9 °C and pH 3.8 for CMCase and 52.8 °C and pH 4.8 for β-glucosidase, respectively.

Fungal lignocellulolytic enzymes and lignocellulose: A critical review on their contribution to multiproduct biorefinery and global biofuel research

The continuous increase in the global energy demand has diminished fossil fuel reserves and elevated the risk of environmental deterioration and human health. Biorefinery processes involved in producing bio-based energy-enriched chemicals have paved way to meet the energy demands. Compared to the thermochemical processes, fungal system biorefinery processes seems to be a promising approach for lignocellulose conversion. It also offers an eco-friendly and energy-efficient route for biofuel generation. Essentially, ligninolytic white-rot fungi and their enzyme arsenals degrade the plant biomass into structural constituents with minimal by-products generation. Hemi- or cellulolytic enzymes from certain soft and brown-rot fungi are always favoured to hydrolyze complex polysaccharides into fermentable sugars and other value-added products. However, the cost of saccharifying enzymes remains the major limitation, which hinders their application in lignocellulosic biorefinery. In the past, research has been focused on the role of lignocellulolytic fungi in biofuel production; however, a cumulative study comprising the contribution of the lignocellulolytic enzymes in biorefinery technologies is still lagging. Therefore, the overarching goal of this review article is to discuss the major contribution of lignocellulolytic fungi and their enzyme arsenal in global biofuel research and multiproduct biorefinery.

Enzymatic hydrolysis of lignocellulosic biomass using native cellulase produced by Aspergillus niger ITV02 under liquid state fermentation

The objective of this work was to evaluate the biochemical characteristics of an enzymatic extract obtained from autochthonous fungus Aspergillus niger ITV02 and its application in the enzymatic hydrolysis of wheat straw and corn stubble pretreated by steam explosion. The enzymatic extract was obtained by submerged fermentation using delignified sweet sorghum bagasse as a carbon source. The results obtained showed that the enzymatic extract had β-glucosidase and endoglucanase activities. The effects of pH and temperature on cellulase activity were evaluated and its thermostability was determined. The optimal parameters of the β-glucosidase and endoglucanase activities obtained were pH 5 and 70 °C. The enzymatic extract of A. niger ITV02 was used to hydrolyze wheat straw and corn stubble, and the hydrolysis yields were compared with those obtained by a commercial cellulase (Celluclast 1.5L NS 50013) and CellicCTec3. The results showed that with the use the mixture of Celluclast 1.5L-A. niger ITV02 and CellicCTec3-A. niger ITV02 in the hydrolysis, conversions of 86.36% and 67.8% were obtained, respectively. Glucose production for the mixture extract increased 2.15 times more than when the enzyme was used independently alone. The present work shows that A. niger ITV02 has a potential as an enzyme producer for lignocellulosic hydrolysis.