Evaluation of enhanced production of cellulose deconstructing enzyme using natural and alkali pretreated sugar cane bagasse under the influence of graphene oxide

Review of research progress on the production of cellulase from filamentous fungi

Cellulases have been widely used in many fields such as animal feed, textile, food, lignocellulose bioconversion, etc. Efficient and low-cost production of cellulases is very important for its industrial application, especially in bioconversion of lignocellulosic biomass. Filamentous fungi are currently widely used in industrial cellulase production due to their ability to secrete large amounts of active free cellulases extracellularly. This review comprehensively summarized the research progress on cellulases from filamentous fungi in recent years, including filamentous fungi used for cellulase production and its modification strategies, enzyme compositions, characterization methods and application of fungal cellulase systems, and the production of fungal cellulase includes production processes, factors affecting cellulase production such as inducers, fermentation medium, process parameters and their control strategies. Also, the future perspectives and research topics in fungal cellulase production are presented in the end of the review. The review helps to deepen the understanding of the current status of fungal cellulases, thereby promoting the production technology progress and industrial application of filamentous fungal cellulase.

Cryptococcus laurentii: a wild yeast for xylanase production from agricultural by-products

The development of technologies that allow the production of enzymes at a competitive cost is of great importance for several biotechnological applications, and the use of agro-industrial by-products is an excellent alternative to minimize costs and reduce environmental impacts. This study aimed to produce endo-xylanases using agro-industrial substrates rich in hemicellulose as sources of xylan in culture media. For this purpose, the yeast Cryptococcus laurentti and five lignocellulosic materials (defatted rice bran, rice husk, corn cob, oat husks, and soybean tegument), with and without pretreatment, were used as a source of xylan for enzyme production. To insert the by-products in the culture medium, they were dried and treated (if applicable) with 4% (w.v-1) NaOH and then added in a concentration of 2% (w.v-1). The cultures were agitated for 96 h, and the aliquots were removed to determine the enzymatic activities. Among the by-products studied, the maximum activity (8.7 U. mL-1 at pH 7.3) was obtained where rice bran was used. In contrast, corn cob was the by-product that resulted in lower enzyme production (1.6 U.mL-1). Thus, the defatted rice bran deserves special attention in front of the other by-products used since it provides the necessary substrate for producing endo-xylanases by yeast.

Rice straw derived graphene-silica based nanocomposite and its application in improved co-fermentative microbial enzyme production and functional stability

Cellulases are the one of the most highly demanded industrial biocatalysts due to their versatile applications, such as in the biorefinery industry. However, relatively poor efficiency and high production costs are included as the key industrial constraints that hinder enzyme production and utilization at economic scale. Furthermore, the production and functional efficiency of the β-glucosidase (BGL) enzyme is usually found to be relatively low among the cellulase cocktail produced. Thus, the current study focuses on fungi-mediated improvement of BGL enzyme in the presence of a rice straw-derived graphene-silica-based nanocomposite (GSNCs), which has been characterized using various techniques to analyze its physicochemical properties. Under optimized conditions of solid-state fermentation (SSF), co-fermentation using co-cultured cellulolytic enzyme has been done, and maximum enzyme production of 42 IU/gds FP, 142 IU/gds BGL, and 103 IU/gds EG have been achieved at a 5 mg concentration of GSNCs. Moreover, at a 2.5 mg concentration of nanocatalyst, the BGL enzyme showed its thermal stability at 60°C and 70 °C by holding its half-life relative activity for 7 h, while the same enzyme demonstrated pH stability at pH 8.0 and 9.0 for the 10 h. This thermoalkali BGL enzyme might be useful for the long-term bioconversion of cellulosic biomass into sugar.

Microbial cellulase production and stability investigations via graphene like carbon nanostructure derived from paddy straw

Cellulases are among the most in-demand bioprocess enzymes, and the high cost of production, combined with their low enzymatic activity, is the main constraint, particularly in the biofuels industry. As a result, low-cost enzyme production modes with high activity and stability have emerged as the primary focus of research. Here, a method for producing a graphene like carbon nanostructure (GLCNs) has been investigated utilizing paddy straw (Ps), and its physicochemical characteristics have been examined using a variety of techniques including XRD, FT-IR, SEM and TEM. Further, the pretreatment of Ps feedstock for cellulase production was done using diluted waste KOH liquid collected during the preparation of the GLCNs. To increase the production and stability of the enzyme, newly prepared GLCNs is utilized as a nanocatalyst. Using 15 mg of GLCNs, 35 IU/gds FP activity was seen after 72 h, followed by 158 IU/gds EG and 114 IU/gds BGL activity in 96 h. This nanocatalyst supported enzyme was thermally stable at 70 °C up to 15 h and exhibited stability at pH 7.0 for 10 h by holding 66 % of its half-life.

Improvement of Lignocellulolytic Enzyme Production Mediated by Calcium Signaling in Bacillus subtilis Z2 under Graphene Oxide Stress

An increase in exoenzyme production can be enhanced by environmental stresses such as graphene oxide (GO) stress, but the link between the two events is still unclear. In this work, the effect of GO as an environmental stress factor on exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) biosynthesis was investigated in Bacillus subtilis Z2, and a plausible mechanism by which cytosolic Ca²⁺ regulates lignocellulolytic enzyme production in B. subtilis Z2 subjected to GO stress was proposed. The filter paper-hydrolyzing (FPase [representing total cellulase]), carboxymethylcellulase (CMCase [representing endoglucanase]), and β-glucosidase activities and extracellular protein concentration of the wild-type strain under 10 μg/mL GO stress were 1.37-, 1.64-, 1.24-, and 1.16-fold those of the control (without GO stress), respectively. Correspondingly, the transcription levels of lignocellulolytic enzyme genes, cytosolic Ca²⁺ level, and biomass concentration of B. subtilis were all increased. With lignocellulolytic enzyme from B. subtilis used to hydrolyze alkali-pretreated rice straw, the released reducing sugar concentration reached 265.53 mg/g, and the removal rates of cellulose, hemicellulose, and lignin were 52.4%, 30.1%, and 7.5%, respectively. Furthermore, transcriptome data revealed that intracellular Ca²⁺ homeostasis played a key role in regulating the levels of gene transcription related to the synthesis of lignocellulolytic enzymes and exoenzymes. Finally, the use of Ca²⁺ inhibitors (LaCl₃ and EDTA) and deletion of spcF (a calmodulin-like protein gene) further demonstrated that the overexpression of those genes was regulated via calcium signaling in B. subtilis subjected to GO stress. IMPORTANCE To effectively convert lignocellulose into fermentable sugars, high lignocellulolytic enzyme loading is needed. Graphene oxide (GO) has been shown to promote exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) production in some microorganisms; however, the regulatory mechanism of the biosynthesis of lignocellulolytic enzymes under GO stress remains unclear. In this work, the lignocellulolytic enzyme production of B. subtilis under GO stress was investigated, and the potential mechanism by which B. subtilis enhanced lignocellulolytic enzyme production through the calcium signaling pathway under GO stress was proposed. This work revealed the role of calcium signaling in the production of enzymes under external environmental stress and provided a direction to facilitate lignocellulolytic enzyme production by B. subtilis.

Improved biohydrogen production via graphene oxide supported granular system based on algal hydrolyzate, secondary sewage sludge and bacterial consortia

Biohydrogen production using renewable sources has been regarded as one of the most sustainable ways to develop low-cost and green production technology. In order to achieve this objective, herein biohydrogen production has been conducted using the combination of untreated secondary sewage sludge (Sss), algal biomass hydrolyzate (Abh), graphene oxide (GO) and bacterial consortia that forms a granular system. Thus, naturally formed granular system produced cumulative H₂ of 1520mL/L in 168h with the maximum production rate of 13.4mL/L/h in 96h at initial pH 7.0, and optimum temperature of 37^oC. It is noticed that the combination of Abh, Sss and GO governed medium showed 42.05% higher cumulative H₂ production along with 22.71% higher production rate as compared to Abh and Sss based H₂ production medium. The strategy presented herein may find potential applications for the low-cost biohydrogen production using waste biomasses including Sss and Abh.

Preparation of photoluminescent and anticorrosive epoxy paints immobilized with nanoscale graphene from sugarcane bagasse agricultural waste

Sugarcane bagasse agricultural waste has been one of the most common solid pollutants worldwide. Thus, introducing a simple method to convert sugarcane bagasse into value-added materials has been highly significant. Herein, we develop a simple and green strategy to reprocess sugarcane bagasse as a starting material for the preparation of graphene oxide nanosheets toward the preparation of novel photoluminescent, hydrophobic, and anticorrosive epoxy nanocomposite coatings integrated with lanthanide-doped aluminate nanoparticles. Environmentally friendly graphene oxide (GO) nanostructures were provided by a single-step preparation procedure from sugarcane bagasse (SCB) agricultural waste using ferrocene-based oxidation under muffled conditions. The oxidized SCB nanostructures were applied as a drier, anticorrosion, and crosslinking agent for epoxy coatings. Different concentrations of pigment phosphor were applied onto the epoxy coating. The generated epoxy-graphene-aluminate (EGA) paints were then coated onto mild steel. The hydrophobic properties and hardness as well as resistance to scratch of the EGA paints were examined. The transparency and colorimetric screening of the EGA nanocomposite paints were determined by the absorption spectral analysis and CIE Lab parameters. The luminescent translucent paints demonstrated a bright green emission at 520 nm when excited at 372 nm. The anticorrosion properties of the painted steel submerged in NaCl_(aq) were inspected by the electrochemical impedance spectral (EIS) method. The EGA paints with phosphor (11% w/w) exhibited the most distinct anti-corrosion properties and long-persistent luminescence. The produced paints displayed high durability and photostability.