Optimization of upstream and downstream process parameters for cellulase-poor-thermo-solvent-stable xylanase production and extraction by Aspergillus tubingensis FDHN1

Application of Immobilized β-Glucosidase from Candida boidinii in the Hydrolysis of Delignified Sugarcane Bagasse

Candida boidinii is a methylotrophic yeast with wide geographical distribution. In the present study, the microorganism was isolated from the Bahian semiarid and the enzymatic extract containing β-glucosidase was obtained through submerged fermentation. Response surface methodology was employed to optimize of fermentation medium. The higher production of β-glucosidase was obtained after 71 h of fermentation in an optimized medium composed of 3.35% glucose, 1.78% yeast extract and 1% peptone. The optimum pH and temperature of enzymatic activity were 6.8 (citrate-phosphate buffer) and 71.7 °C, respectively. Salts tested (10 mM) CaCl2, Na2SO4 and ZnSO4 promotes the increase of 91%, 45% and 80% of activity, respectively. The enzyme retained 64% ± 2.3 of its initial activity after 1 h heating at 90 °C. The production of reducing sugars was 95.94% after 24 h of hydrolysis and, with the addition of metal ions, this value increased more than 2 times. Among the supports analyzed for immobilization, chitosan showed higher residual activity during reuse. The immobilized enzyme showed higher activity at 60 °C with pH 6 and preserved almost 100% of the initial activity after 30 min at 70 °C.

Leaching Approach for β-Glucosidase Extraction from Fermented Rice Husk in Solid State Cultivation by Aspergillus protuberus

Environmental problems are caused by the disposal of agrowastes in developing countries. It is imperative to convert such wastes into useful products, which require enzymes such as β-glucosidase. β-Glucosidase has variety of applications in biotechnology including food, textile, detergents, pulp and paper, pharmaceutical and biofuel industries. β-Glucosidase production was performed using the locally isolated Aspergillus protuberus using best growth circumstances on rice husk in solid-state fermentation (SSF). Leaching of β-glucosidase from fermented rice husk with number of solvents to evaluate their extraction efficacy. Among the different solvents examined, acetate buffer (0.02 M, pH 5.0) proved to be the best solvent. The subsequent parameters were optimized with acetate buffer. Two washes with acetate buffer each by shaking (30 min) in a ratio of 1 g of rice husk: 5 ml of acetate buffer together attained maximum recovery of β-glucosidase with 41.95 U/g of rice husk.

An insight into microbial sources, classification, and industrial applications of xylanases: A rapid review

Endo 1,4-β-d-xylanases (EC3.2.1.8) are one of the key lignocellulose hydrolyzing enzymes. Xylan, which is present in copious amounts on earth, forms the primary substrate of endo-xylanases, which can unchain the constituent monosaccharides linked via β-1,4-glycosidic bonds from the xylan backbone. Researchers have shown keen interest in the xylanases belonging to glycoside hydrolase families 10 and 11, whereas those placed in other glycoside hydrolase families are yet to be investigated. Various microbes such as bacteria and fungi harbor these enzymes for the metabolism of their lignocellulose fibers. These microbes can be used as miniature biofactories of xylanase enzymes for a plethora of environmentally benign applications in pulp and paper industry, biofuel production, and for improving the quality of food in bread baking and fruit juice industry. This review highlights the potential of microbes in production of xylanase for industrial biotechnology.

Cost-effective production of biocatalysts using inexpensive plant biomass: a review

Enzymes are the complex protein moieties, catalyze the rate of chemical reactions by transforming various substrates to specific products and play an integral part in multiple biochemical cycles. Advancement in enzyme research and its integration with industries have reformed the biotech industries. It provides a superior monetary and ecological exchange to traditional material measures in an efficient and environmentally sustainable manner. The cost-effective production of pure and highly active enzymes is still a challenge for the biocatalyst industries. The use of high purity substrates further raises the cost of a typical biocatalyst. The use of low-cost plant-based biomasses as an enticing and sustainable substrate for enzyme production is the most cost-effective approach to these problems. Given the relevance of biomass as a substrate for enzyme development, this review article focuses on the key source, composition and major enzyme generated using various biomass residues. Furthermore, the difficulties associated with the use of biomass as a substrate and technical developments in this area, are also addressed. The use of waste biomass as a substrate lowers the ultimate cost for the production of biocatalysts while simultaneously reduces the waste burden from the environment.

Biochemical characterization and enhanced production of endoxylanase from thermophilic mould Myceliophthora thermophila

Endoxylanase production from M. thermophila BJTLRMDU3 using rice straw was enhanced to 2.53-fold after optimization in solid state fermentation (SSF). Endoxylanase was purified to homogeneity employing ammonium sulfate precipitation followed by gel filtration chromatography and had a molecular mass of ~ 25 kDa estimated by SDS-PAGE. Optimal endoxylanase activity was recorded at pH 5.0 and 60 °C. Purified enzyme showed complete tolerance to n-hexane, but activity was slightly inhibited by other organic solvents. Among surfactants, Tweens (20, 60, and 80) and Triton X 100 slightly enhanced the enzyme activity. The V_max and K_m values for purified endoxylanase were 6.29 µmol/min/mg protein and 5.4 mg/ml, respectively. Endoxylanase released 79.08 and 42.95% higher reducing sugars and soluble proteins, respectively, which control after 48 h at 60 °C from poultry feed. Synergistic effect of endoxylanase (100 U/g) and phytase (15 U/g) on poultry feed released higher amount of reducing sugars (58.58 mg/feed), soluble proteins (42.48 mg/g feed), and inorganic phosphate (28.34 mg/feed) in contrast to control having 23.55, 16.98, and 10.46 mg/feed of reducing sugars, soluble proteins, and inorganic phosphate, respectively, at 60 °C supplemented with endoxylanase only.

Integrated process development: The key to improve Fab production in E. coli

Bioprocess development and optimization is a challenging, costly, and time-consuming effort. In this multidisciplinary task, upstream processing (USP) and downstream processing (DSP) are conventionally considered distinct disciplines. This consideration fosters "one-way" optimization disregarding interdependencies between unit operations; thus, the full potential of the process chain cannot be achieved. Therefore, it is necessary to fully integrate USP and DSP process development to provide balanced biotechnological production processes. The aim of the present study was to investigate how different host/secretory signal/antigen binding fragment (Fab) combinations in E. coli expression systems influence USP, primary recovery performance and the final product quality. We ran identical fed-batch cultivations with 16 different expression clones to study growth and product formation kinetics, as well as centrifugation efficiency, viscosity, extracellular DNA, and endotoxin content, important parameters in DSP. We observed a severe influence on cell growth, product titer, extracellular product, and cell lysis, accompanied by a significant impact on the analyzed parameters of DSP performance. Our results provide the basis for future research on integrated process development considering interdependencies between USP and DSP; however, individual products need to be considered specifically. These interdependencies need to be understood for rational decision-making and efficient process development in research and industry.

Efficient enzymatic saccharification of alkaline and ionic liquid-pretreated bamboo by highly active extremozymes produced by the co-culture of two halophilic fungi

Herein, we studied two strains of halophilic fungi (Aspergillus flavus and Aspergillus penicillioides) as potential potent sources of hydrolases under solid-state fermentation conditions. We found that the co-culture of these two fungal species was associated with maximal CMCase, FPase, xylanase, and β-xylosidase activity under optimized fermentation conditions. These enzymes functioned optimally at pH values from 9.0 to 10.0, at temperatures from 50 °C to 60 °C, and in the presence of 15-20% NaCl. These enzymes were also stable in metal salt solutions and the presence of ionic liquids. Reducing sugar yields following the cellulase-hemicellulase co-treatment of untreated, alkaline-pretreated, and ionic liquid-pretreated bamboo were higher than those associated with separate cellulase and hemicellulase treatments, thus confirming the synergistic activity of cellulase-hemicellulase co-treatment in the context of bamboo saccharification. These results indicate that these two fungi are promising hydrolase producers that can facilitate the bioconversion of bamboo biomass.

Taguchi optimization and scale up of xylanase from Bacillus licheniformis isolated from hot water geyser

BACKGROUND

Xylanase is one of the widely applied industrial enzymes with diverse applications. Thermostability and alkali tolerance are the two most desirable qualities for industrial applications of xylanase. In this paper, we reveal the statistical Taguchi optimization strategy for maximization of xylanase production. The important process parameters pH, temperature, concentration of wheat bran, and concentration of yeast extract were optimized using the Taguchi L8 orthogonal array where the 4 factors were considered at 2 levels (high and low).

RESULTS

The optimized conditions given by model were obtained as follows: (i) pH 6, (ii) culture temperature 35 °C, (iii) concentration of xylan 2% w/v, (iv) concentration of wheat bran 2.5% w/v. The production was scaled upto 2.5 L bioreactor using optimized process parameters. A high xylanase titer of 400 U/ml could be achieved in less than 60 h of culture in the reactor.

CONCLUSION

Optimization was successful in achieving about threefold increase in the yield of xylanase. The optimized conditions resulted in a successful scale up and enhancement of xylanase production.

Development of novel economical methodologies for zymographic analysis of purified xylano-pectinolytic enzymes using agrowaste-based substrates

In this study, zymographic analysis for xylanase and pectinase enzymes has been carried out using agrowaste residues, wheat bran and citrus peel as well as their extracts. Isozymic forms of xylanase as well as pectinase enzyme displayed comparable zymographic bands onto agar petriplates containing either commercial substrates (xylan and pectin), agrowaste-based substrates (wheat bran and citrus peel), or polysaccharides extracted from these agrowastes (crude xylan and pectin extracted from wheat bran and citrus peel, respectively), indicating the fact that agro residues and their extracts can be utilized as a substitute of cost-intensive commercial substrates, xylan and pectin for zymographic analysis. This is the first report revealing the zymographic analysis of xylano-pectinolytic enzymes using agro-based solid residues particles or polysaccharides extracted from agro-based residues.

Amylase and Xylanase from Edible Fungus Neurospora intermedia: Production and Characterization

Integrated enzyme production in the biorefinery can significantly reduce the cost of the entire process. The purpose of the present study is to evaluate the production of two hydrolyzing enzymes (amylase and xylanase) by an edible fungus used in the biorefinery, Neurospora intermedia. The enzyme production was explored through submerged fermentation of synthetic media and a wheat-based waste stream (thin stillage and wheat bran). The influence of a nitrogen source on N. intermedia was investigated and a combination of NaNO₃ and yeast extract has been identified as the best nitrogen source for extracellular enzyme production. N. intermedia enzymes showed maximum activity at 65 °C and pH around 5. Under these conditions, the maximum velocity of amylase and xylanase for starch and xylan hydrolysis was found to be 3.25 U mL⁻¹ and 14.77 U mL⁻¹, respectively. Cultivation of N. intermedia in thin stillage and wheat bran medium resulted in relatively high amylase (8.86 ± 0.41 U mL⁻¹, 4.68 ± 0.23) and xylanase (5.48 ± 0.21, 2.58 ± 0.07 U mL⁻¹) production, respectively, which makes this fungus promising for enzyme production through a wheat-based biorefinery.

Biosynthesis, molecular modeling and statistical optimization of xylanase from a mangrove associated actinobacterium Streptomyces variabilis (MAB3) using Box-Behnken design with its bioconversion efficacy

The present study was undertaken to evaluate the biosynthesis, molecular modeling and statistical optimization of xylanase production through Box-Behnken design by a mangrove associated actinobacterium Streptomyces variabilis (MAB3). Initially, the production of xylanase by the selected strain was carried through submerged fermentation using birchwood xylan as substrate. Further the xylanase production was statistically optimized through Box-Behnken design. It showed 5.30 fold increase of xylanase production by the isolate compared to 'one factor at a time approach' in the presence of the basal medium containing birchwood xylan (2.0% w/v) at pH 8.2, temperature 46.5 °C, inoculum size of 2% for 68 h. The analysis of variance (ANOVA) revealed high coefficient of determination (R² = 0.9490) for the respective responses at significant level (P < 0.0001). The xylanase was purified by different purification steps and it resulted 5.30 fold increase with the yield of 21.27% at the final step using sephadex G-75 chromatography. The molecular weight of the purified xylanase was observed as 50 kDa on 10% SDS-PAGE. The homology 3D structure of the purified xylanase protein was predicted and this protein encodes with 420 amino acid residues. The maximum activity of purified xylanase was observed at pH 8, temperature 40 °C and the production medium supplemented with 1 mM Ca²⁺ metal ion, 2.0% xylan and 1.5% NaCl. The kinetic parameters of the purified xylanase expressed the K_m and V_max values of 5.23 mg/ml and 152.07 μg/min/mg, respectively. Finally, the xylanolytic hydrolysis of pretreated agro-residues, especially the rice straw substituted medium yielded maximum (46.28 mg/g) level of reducing sugar and saccharification (63.18%), followed by bioethanol production (3.92 g/l) at 72 h of incubation. Based on the results, it could be confirmed that the selected isolate is a potent strain for xylanase production and also it can able to convert the pretreated agro-residues into economically important byproduct like bioethanol.

Characterization of cellulase from Aspergillus tubingensis NKBP-55 for generation of fermentable sugars from agricultural residues

The aim of this work was to characterize cellulase from Aspergillus tubingensis NKBP-55 for generation of fermentable sugars from agricultural residues. The strain produced high titres of cellulase (750 U/gds) on copra meal in solid state fermentation (SSF). The enzyme preparation also showed hemicellulolytic activities (U/gds) viz. endo-mannanase (1023), endo-xylanase (167), β-glucosidase (72) and α-galactosidase (54). Zymography revealed presence of six cellulases, six mannanases and one β-glucosidase. It effectively degraded sugarcane bagasse (SCB) and rice straw (RS) releasing xylose, glucose and cellobiose. One cellulase (Cat 1, Mr ∼65 kDa) was purified and characterized. It retained more than 50% activity at 70 °C after 150 mins and its activity was enhanced in the presence of Mn²⁺ ions (130%) and β-mercaptoethanol (140%). FTIR and ¹³C CP/MAS NMR analysis of the enzyme treated SCB and RS revealed degradation of cellulose and hemicellulose, while ¹H and ¹³C liquid state NMR experiments confirmed release of glucose.

The novel oleaginous bacterium Sphingomonas sp. EGY1 DSM 29616: a value added platform for renewable biodiesel

Oleaginous microorganisms are regarded as efficient, renewable cell factories for lipid biosynthesis, a biodiesel precursor, to overwhelm the cosmopolitan energy crisis with affordable investment capital costs. Present research highlights production and characterization of lipids by a newly isolated oleaginous bacterium, Sphingomonas sp. EGY1 DSM 29616 through an eco-friendly approach. Only sweet whey [42.1% (v/v)] in tap water was efficiently used as a growth medium and lipid production medium to encourage cell growth and trigger lipid accumulation simultaneously. Cultivation of Sphingomonas sp. EGY1 DSM 29616 in shake flasks resulted in the accumulation of 8.5 g L^-1 lipids inside the cells after 36 h at 30 °C. Triglycerides of C16:C18 saturated and unsaturated fatty acids showed a similar pattern to tripalmitin or triolein; deduced from gas chromatography (GC), thin layer chromatography (TLC), and Matrix-assisted laser desorption/ionization time-of-flight-mass spectra analysis (MALDI-TOF-MS) analyses. Batch cultivation 2.5 L in a laboratory scale fermenter led to 13.8 g L^-1 accumulated lipids after 34 h at 30 °C. Present data would underpin the potential of Sphingomonas sp. EGY1 DSM 29616 as a novel renewable cell factory for biosynthesis of biodiesel.

Xylanase production from Penicillium citrinum isolate HZN13 using response surface methodology and characterization of immobilized xylanase on glutaraldehyde-activated calcium-alginate beads

The present study reports the production of high-level cellulase-free xylanase from Penicillium citrinum isolate HZN13. The variability in xylanase titers was assessed under both solid-state (SSF) and submerged (SmF) fermentation. SSF was initially optimized with different agro-waste residues, among them sweet sorghum bagasse was found to be the best substrate that favored maximum xylanase production (9643 U/g). Plackett–Burman and response surface methodology employing central composite design were used to optimize the process parameters for the production of xylanase under SSF. A second-order quadratic model and response surface method revealed the optimum conditions for xylanase production (sweet sorghum bagasse 25 g/50 ml; ammonium sulphate 0.36 %; yeast extract 0.6 %; pH 4; temperature 40 °C) yielding 30,144 U/g. Analysis of variance (ANOVA) showed a high correlation coefficient (R² = 97.63 %). Glutaraldehyde-activated calcium-alginate-immobilized purified xylanase showed recycling stability (87 %) up to seven cycles. Immobilized purified xylanase showed enhanced thermo-stability in comparison to immobilized crude xylanase. Immobilization kinetics of crude and purified xylanase revealed an increase in K_m (12.5 and 11.11 mg/ml) and V_max (12,500 and 10,000 U/mg), respectively. Immobilized (crude) enzymatic hydrolysis of sweet sorghum bagasse released 8.1 g/g (48 h) of reducing sugars. Xylose and other oligosaccharides produced during hydrolysis were detected by High-Performance Liquid Chromatography. The biomass was characterized by Scanning Electron Microscopy, Energy Dispersive X-ray and Fourier Transformation Infrared Spectroscopy. However, this is one of the few reports on high-level cellulase-free xylanase from P. citrinum isolate using sweet sorghum bagasse.

Purification, characterization, gene cloning and expression of GH-10 xylanase (Penicillium citrinum isolate HZN13)

An extracellular thermostable xylanase (Xyl-IIb) produced by Penicillium citrinum isolate HZN13 was purified to homogeneity using DEAE-Sepharose, Sephadex G-100 and Bio-Gel P-60 chromatography with specific activity of 6272.7 U/mg and 19.6-fold purification. The purification revealed the occurrence of multiple forms of xylanases (Xyl-I, Xyl-IIa, Xyl-IIb and Xyl-III). The molecular mass of highly purified Xyl-IIb was ~31 kDa with SDS-PAGE. The enzyme was cellulase-free, thermostable (55–75 °C) and acidophilic (3.5–5.0). It was activated by Ca²⁺, Ba²⁺, DTT and β-mercaptoethanol, whereas inhibited by Hg²⁺, Pb²⁺, Ni²⁺ and p-CMB. Purified Xyl-IIb exhibited highest specificity toward birchwood and oat spelts xylan. Kinetics of Xyl-IIb revealed a K_m of 10 mg/ml and 16.7 mg/ml and V_max of 9523g and 15,873 U/mg with birchwood and oat spelts xylan, respectively, indicating high affinity toward birchwood xylan. The xylanase (Xyl-IIb) belongs to glycosyl hydrolase (GH) family 10 based on conserved regions. Xylanase-encoding gene (xynB) consists of 1501 bp with an open reading frame of 264 bp which was predicted to encode a protein having 87 amino acids and shared homology with endo-1,4-beta-xylanase (xynB) gene from Penicillium citrinum. Cloned xynB gene was expressed in E. coli BL21 (DE3) with xylanase activity (80 U/mg) and confirmed to be GH-10 Xyl-IIa based on molecular mass (~40 kDa). These properties of xylanase make it promising for their applications in biofuel industries.

Optimization of Xylanase Production through Response Surface Methodology by Fusarium sp. BVKT R2 Isolated from Forest Soil and Its Application in Saccharification

Xylanses are hydrolytic enzymes with wide applications in several industries like biofuels, paper and pulp, deinking, food, and feed. The present study was aimed at hitting at high yield xylanase producing fungi from natural resources. Two highest xylanase producing fungal isolates-Q12 and L1 were picked from collection of 450 fungal cultures for the utilization of xylan. These fungal isolates-Q12 and L1 were identified basing on ITS gene sequencing analysis as Fusarium sp. BVKT R2 (KT119615) and Fusarium strain BRR R6 (KT119619), respectively with construction of phylogenetic trees. Fusarium sp. BVKT R2 was further optimized for maximum xylanase production and the interaction effects between variables on production of xylanase were studied through response surface methodology. The optimal conditions for maximal production of xylanase were sorbitol 1.5%, yeast extract 1.5%, pH of 5.0, Temperature of 32.5°C, and agitation of 175 rpm. Under optimal conditions, the yields of xylanase production by Fusarium sp. BVKT R2 was as high as 4560 U/ml in SmF. Incubation of different lignocellulosic biomasses with crude enzyme of Fusarium sp. BVKT R2 at 37°C for 72 h could achieve about 45% saccharification. The results suggest that Fusarium sp. BVKT R2 has potential applications in saccharification process of biomass.