Isolation, screening and characterization of a novel extracellular xylanase from A spergillus niger (KP874102.1) and its application in orange peel hydrolysis

High-Molecular-Weight Xylanase from B. pumilus US570 Strain: Purification, Characterization and Application in Banana and Orange Peels Hydrolysis and Breadmaking

New xylanase (XylUS570) was purified from the Bacillus pumilus US570 strain. It has a molecular mass of about 232 kDa. This is the first report on the highest molecular weight monomeric xylanase produced by bacteria. The optimum pH and temperature recorded for enzyme activity were 7 and 55 °C, respectively with a half-life time of 10 min at 60 °C. At 37 °C, the enzyme retains more than 50% of its activity at a pH ranging from 6 to 9.5 for 24 h. The XylUS570 exhibited a high activity on xylan, but no activity was detected for cellulosic substrates. The Vmax and Km values exhibited by the purified enzyme on beechwood xylan were 37.05 U mL-1 and 4.189 mg mL-1, respectively. The XylUS570 was used in banana and orange peels hydrolysis and showed potential efficiency to liberate reducing sugars. It could be a good candidate for bio-ethanol production from fruit waste. The purified enzyme was used also as an additive in breadmaking. A decrease in water absorption, an increase in dough rising and improvements in volume and specific volume of the bread were recorded.

High-level production of xylose from agricultural wastes using GH11 endo-xylanase and GH43 β-xylosidase from Bacillus sp

As a promising feedstock, alkali-extracted xylan from lignocellulosic biomass is desired for producing xylose, which can be used for renewable biofuels production. In this study, an efficient pathway has been established for low-cost and high-yield production of xylose by hydrolysis of alkali-extracted xylan from agricultural wastes using an endo-1,4-xylanase (XYLA) from Bacillus safensis TCCC 111022 and a β-xylosidase (XYLO) from B. pumilus TCCC 11573. The optimum activities of recombinant XYLA (rXYLA) and XYLO (rXYLO) were 60 ℃ and pH 8.0, and 30 ℃ and pH 7.0, respectively. They were stable over a broad pH range (pH 6.0-11.0 and 7.0-10.0). rXYLO showed a relatively high xylose tolerance up to 100 mM. Furthermore, the yield of xylose from wheat straw, rice straw, corn stover, corncob and sugarcane bagasse by rXYLA and rXYLO was 63.77%, 71.76%, 68.55%, 53.81%, and 58.58%, respectively. This study demonstrated a strategy to produce xylose from agricultural wastes by integrating alkali-extracted xylan and enzymatic hydrolysis.

Novel thermo-alkali-stable cellulase-producing Serratia sp. AXJ-M cooperates with Arthrobacter sp. AXJ-M1 to improve degradation of cellulose in papermaking black liquor

There is an urgent requirement to treat cellulose present in papermaking black liquor since it induces severe economic wastes and causes environmental pollution. We characterized cellulase activity at different temperatures and pH to seek thermo-alkali-stable cellulase-producing bacteria, a natural consortium of Serratia sp. AXJ-M and Arthrobacter sp. AXJ-M1 was used to improve the degradation of cellulose. Notably, the enzyme activities and the degradation rate of cellulose were increased by 30%-70% and 30% after co-culture, respectively. In addition, the addition of cosubstrates increased the degradation rate of cellulose beyond 30%. The thermo-alkali-stable endoglucanase (bcsZ) gene was derived from the strain AXJ-M and was cloned and expressed. The purified bcsZ displayed the maximum activity at 70 °C and pH 9. Mn²⁺, Ca²⁺, Mg²⁺ and Tween-20 had beneficial effects on the enzyme activity. Structurally, bcsZ potentially catalyzed the degradation of cellulose. The co-culture with ligninolytic activities significantly decreased target the parameters (cellulose 45% and COD 95%) while using the immobilized fluidized bed reactors (FBRs). Finally, toxicological tests and antioxidant enzyme activities indicated that the co-culture had a detoxifying effect on black liquor. Our study showed that Serratia sp. AXJ-M acts synergistically with Arthrobacter sp. AXJ-M1 may be potentially useful for bioremediation for black liquor.

Improvement of XYL10C_∆N catalytic performance through loop engineering for lignocellulosic biomass utilization in feed and fuel industries

BACKGROUND

Xylanase, an important accessory enzyme that acts in synergy with cellulase, is widely used to degrade lignocellulosic biomass. Thermostable enzymes with good catalytic activity at lower temperatures have great potential for future applications in the feed and fuel industries, which have distinct demands; however, the potential of the enzymes is yet to be researched.

RESULTS

In this study, a structure-based semi-rational design strategy was applied to enhance the low-temperature catalytic performance of Bispora sp. MEY-1 XYL10C_∆N wild-type (WT). Screening and comparisons were performed for the WT and mutant strains. Compared to the WT, the mutant M53S/F54L/N207G exhibited higher specific activity (2.9-fold; 2090 vs. 710 U/mg) and catalytic efficiency (2.8-fold; 1530 vs. 550 mL/s mg) at 40 °C, and also showed higher thermostability (the melting temperature and temperature of 50% activity loss after 30 min treatment increased by 7.7 °C and 3.5 °C, respectively). Compared with the cellulase-only treatment, combined treatment with M53S/F54L/N207G and cellulase increased the reducing sugar contents from corn stalk, wheat bran, and corn cob by 1.6-, 1.2-, and 1.4-folds, with 1.9, 1.2, and 1.6 as the highest degrees of synergy, respectively.

CONCLUSIONS

This study provides useful insights into the underlying mechanism and methods of xylanase modification for industrial utilization. We identified loop2 as a key functional area affecting the low-temperature catalytic efficiency of GH10 xylanase. The thermostable mutant M53S/F54L/N207G was selected for the highest low-temperature catalytic efficiency and reducing sugar yield in synergy with cellulase in the degradation of different types of lignocellulosic biomass.

Beauveria bassiana Xylanase: Characterization and Wastepaper Deinking Potential of a Novel Glycosyl Hydrolase from an Endophytic Fungal Entomopathogen

Beauveria bassiana is an entomopathogenic fungus widely used as a biopesticide for insect control; it has also been shown to exist as an endophyte, promoting plant growth in many instances. This study highlights an alternative potential of the fungus; in the production of an industrially important biocatalyst, xylanase. In this regard, Beauveria bassiana SAN01 xylanase was purified to homogeneity and subsequently characterized. The purified xylanase was found to have a specific activity of 324.2 U·mg⁻¹ and an estimated molecular mass of ~37 kDa. In addition, it demonstrated optimal activity at pH 6.0 and 45 °C while obeying Michaelis–Menton kinetics towards beechwood xylan with apparent K_m, V_max and k_cat of 1.98 mg·mL⁻¹, 6.65 μM·min⁻¹ and 0.62 s⁻¹ respectively. The enzyme activity was strongly inhibited by Ag²⁺ and Fe³⁺ while it was significantly enhanced by Co²⁺ and Mg²⁺. Furthermore, the xylanase was shown to effectively deink wastepaper at an optimal rate of 106.72% through its enzymatic disassociation of the fiber-ink bonds as demonstrated by scanning electron microscopy and infrared spectroscopy. This is the first study to demonstrate the biotechnological application of a homogeneously purified glycosyl hydrolase from B. bassiana.

Bioprocessing of waste biomass for sustainable product development and minimizing environmental impact

Growing concerns around the generation of biomass waste have triggered conversation around sustainable utilization of these seemingly waste materials as feedstock towards energy generation and production of chemicals and other value-added products. Thus, biotechniques such as utilization of microbes and enzymes derived thereof have become important avenues for green pretreatment and conversion of biomass wastes. Although the products of these bioconversions are greener at an overall level, their consumption and utilization still impact the environment. Hence it is important to understand the overall impact from cradle to grave through lifecycle assessment (LCA) techniques and find avenues of process optimization and better utilization of all the materials and products involved. Another factor to consider is overall cost optimization to make the process economically feasible, profitable and increase industrial adoption. This review brings forward these critical aspects to provide better understanding for the advancement of bioeconomy.

Enzymatic characteristics of a recombinant protease (rPepD) from Aspergillus niger expressed in Pichia pastoris

The Aspergillus niger AS3.350 protease gene (pepD) was successfully cloned and expressed in Pichia pastoris KM71. The rPepD activity was 331.5 U/ml, and the optimum temperature and pH were 45 °C and 8-9 respectively. In addition, enzyme activity was significantly inhibited by PMSF, EDTA, Mg²⁺, Fe²⁺ and Zn²⁺ ions, and stimulated by Ca²⁺ which selectively bound to the T³⁰² and D³²³ residues. Mutation in either or both of the residues inhibited rPepD expression, indicating that binding to Ca²⁺ is necessary for PepD expression and activity. The rPepD showed a wide substrate range, and was particularly selective to those with hydrophobic amino acids. The degree of rPepD-mediated hydrolysis of soy protein isolate, corn flour and gluten meal were 8.7%, 38.1% and 33.6% respectively, which was higher than that by Alcalase, indicating that rPepD has potential applications in the food processing industry.

Heterologous expression and characterization of a xylanase and xylosidase from white rot fungi and their application in synergistic hydrolysis of lignocellulose

Endo-xylanase and β-xylosidase are the major enzymes for hemicellulose hydrolysis, which play a significant role in biomass conversion. In our previous work, the white-rot fungi Pleurotus ostreatus HAUCC 162 and Irpex lacteus CD2 were demonstrated to have strong ability in lignocellulose degradation, and the related lignin degradation enzymes were characterized. However, little was known about their hemicellulases. In this work, a novel endo-1, 4-xylanase and a β-xylosidase from Pleurotus ostreatus HAUCC 162 and Irpex lacteus CD2 were heterologously expressed and characterized. The optima of pH and temperature were 5.0 and 55 °C for rXyn162, and 6.5 and 30 °C for rXylCD2. rXyn162 showed high tolerance to metal ions such as Ca²⁺, Cr³⁺, Zn²⁺, Na⁺, and Al³⁺. The recombinant rXyn162 and rXylCD2 exhibited synergistic hydrolysis of oat spelts xylan and sodium hydroxide pretreated cornstalk (SHPC), where the degree of synergy (DS) was 2.26 for SHPC hydrolysis. MALDI-TOF-MS and HPLC analysis showed that xylooligosaccharides (XOS) with small degrees of polymerization (DP2-DP4) were the major XOS hydrolyzate during SHPC degradation by rXyn162 and rXylCD2. In addition, rXyn162 and rXylCD2 could efficiently improve the hydrolysis of SHPC by commercial cellulase. The present study suggested the potential application of rXyn162 and rXylCD2 in the field of biomass pretreatment and biofuel production.

Identification of markers at various stages of batch fermentation and improved production of xylanase using Aspergillus niger (KP874102.1)

Improved xylanase production was carried out through optimization of environmental stresses during spore preservation, seed cultivation and batch fermentation and identifies the markers at various stages. The maximum spore size (radius 6.5 µm) of Aspergillus niger was noticed after 28 days of spore preservation. During seed cultivation, the hypha formed alongside of germination tube (length 196.8 µm) was noticed only at pH-7 after 18 h of incubation at 28 °C. Therefore, pH-7 and 28 °C were considered as optimum during seed cultivation. In this stage, the final pH of the medium was found to be 6.2 which can be used as marker for completion of seed culture. The production media was optimized through Taguchi methodology. The maximum xylanase production was found to be 1575.93 U. The optimum concentration for media components was found to be xylan from beechwood of 3 g/l, potassium nitrate of 10 g/l, magnesium sulphate of 5 g/l, di-potassium hydrogen phosphate of 50 mM, calcium carbonate of 2 g/l, 1000× of trace element (1 ml) and sodium chloride of 5 g/l. It is evident that improved production of xylanase can be possible through optimization of environmental stresses during spore preservation, seed cultivation and batch fermentation and can be intensified through identification of markers at various stages of fermentation process.