Production Of Xylanolytic Enzymes Research Articles

Structure-guided engineering of transcriptional activator XYR1 for inducer-free production of lignocellulolytic enzymes in Trichoderma reesei

The filamentous fungus Trichoderma reesei is widely used for the production of lignocellulolytic enzymes in industry. XYR1 is the major transcriptional activator of cellulases and hemicellulases in T. reesei. However, rational engineering of XYR1 for improved lignocellulolytic enzymes production has been limited by the lack of structure information. Here, alanine 873 was identified as a new potential target for the engineering of XYR1 based on its structure predicted by AlphaFold2. The mutation of this residue to tyrosine enabled significantly enhanced production of xylanolytic enzymes in the medium with cellulose as the carbon source. Moreover, xylanase and cellulase production increased by 56.7- and 3.3-fold, respectively, when glucose was used as the sole carbon source. Under both conditions, the improvements of lignocellulolytic enzyme production were higher than those in the previously reported V821F mutant. With the enriched hemicellulases and cellulases, the crude enzymes secreted by the A873Y mutant strain produced 51 % more glucose and 52 % more xylose from pretreated corn stover than those of the parent strain. The results provide a novel strategy for engineering the lignocellulolytic enzyme-producing capacity of T. reesei, and would be helpful for understanding the molecular mechanisms of XYR1 regulation.

Enhanced Xylanolytic enzyme production from Parthenium hysterophorus through assessment of the RSM tool and their application in saccharification of lignocellulosic biomass

Enhanced Xylanolytic enzyme production from Parthenium hysterophorus through assessment of the RSM tool and their application in saccharification of lignocellulosic biomass

Spartina argentinensis valorization and process optimization for enhanced production of hydrolytic enzymes by filamentous fungus

Hemicellulose is a major component of plant cell walls and xylan is the most predominant polysaccharide. Xylan degrading enzymes integrate the xylanolytic system. Xylanolytic enzymes were produced by fermentation by Aspergillus niger and Thermomyces lanuginosus grown on grass considered unsuitable for farming called Spartina argentinensis . Significant parameters: type of fermentation used (SmF or SSF), type of leaves of S. argentinensis (green or senescent) and conidia final concentration for xylanase production were screened and optimized. The main results showed that the highest levels of xylanolytic enzyme production were obtained by 1 × 10 5 conidia/mL of A. niger in SmF at 96 h, 30ºC, with a mixture of 20.20% of senescent and 79.80% of green leaves. The xylanase specific activity obtained was 62 U/mg, higher than the activity obtained (23 U/mg) in previous work ( Taddia et al., 2019 ), and the concentration of xylanolytic production over that of glucanase activity was maximized five times. The optimized enzymatic extract obtained was characterized by LC-MS and HPLC of carbohydrates. Six enzymes were identified as constituents of the xylanolytic complex and seven carbohydrates. Moreover, the xylanolytic enzyme extract was stable for 30 days at 20 °C. Thus, S. argentinensis can be used within the framework of a circular economy, rendering a synergistic combination of the xylanolytic enzymes with industrial applications. • Lignocellulosic biomass; Spartina argentinensis was utilized in the fermentation. • Enzyme statistical design production was optimized. • Maximum xylanase specific activity of 61 U/mL was obtained. • The enzymatic extract maintained 100% its activity after 30 days at 20°C.

Improvement of cellulosic biomass-degrading enzyme production by reducing extracellular protease production in Aspergillus aculeatus.

We investigated the effects of deleting major extracellular protease-encoding genes on cellulolytic and xylanolytic enzyme production in Aspergillus aculeatus. We first investigated the effect of prtT deletion, a positive transcription factor for extracellular protease-encoding genes in Aspergillus, on extracellular protease production in A. aculeatus. Genetic analysis indicated that among the major extracellular proteases, pepIIa and pepIIb are controlled by PrtT, but pepI is not. Thus, we generated a mutant with deletion of the two genes prtT and pepI (ΔprtTΔpepI) and one with deletion of the three genes pepI, pepIIa, and pepIIb (ΔpepIΔIIaΔIIb). Extracellular protease activities decreased in both ΔprtTΔpepI and ΔpepIΔIIaΔIIb to 3% of that in the control strain (MR12). Comparative time-course analyses indicated that endoglucanase activity in ΔprtTΔpepI increased to double that in MR12. Xylanase activities increased in both ΔprtTΔpepI and ΔpepIΔIIaΔIIb to fourfold higher than that in MR12 at maximum. β-Glucosidase activities were increased in ΔprtTΔpepI and ΔpepIΔIIaΔIIb 1.3- and 1.4-fold higher than that in MR12 at maximum, respectively. Residual activities of endoglucanase, xylanase, and β-glucosidase after 7 days of incubation at 37°C in the culture supernatant were 63%, 36%, and 48% of the original in MR12. Residual endoglucanase activities were more than 80% of the original in ΔprtT, ΔprtTΔpepI, and ΔpepIΔIIaΔIIb. Residual xylanase activities were not improved in all test strains. β-Glucosidase remained almost 97% of the original in ΔprtTΔpepI. These findings indicated that the reduction of extracellular proteases effectively improved cellulolytic and xylanolytic enzyme production and stability in A. aculeatus.

An integrated approach to the sustainable production of xylanolytic enzymes from Aspergillus niger using agro-industrial by-products

Xylanolytic enzymes were produced by Aspergillus niger NRRL3 grown on agro-industrial by-products obtained from the processing of wheat flour without pretreatment. Significant parameters for xylanase production were screened and optimized. The xylanolytic activity obtained in the optimized extract was 138.3 ± 2.6 U/mL, higher than the activity obtained in an unoptimized medium (14.5 ± 0.3 U/mL) in previous work. The optimized fermentation process was performed in a successful 40-fold scale-up. The optimized enzymatic extract obtained was characterized by LC-MS. Nine enzymes were identified as constituents of the xylanolytic complex. Moreover, the xylanolytic enzymes were stable until 60 °C and over a broad range of pH. Sodium, calcium, cobalt and manganese had no inhibitory effect, meanwhile 1% w/v polyvinylpyrrolidone and 1% w/v dextran increased the xylanolytic activity. The saccharification efficiency was evaluated and the surface morphology of the lignocellulosic substrate was monitored by using scanning electron microscopy (SEM). The synergistic combination of the extracted (o purified) xylanolytic enzymes permitted a higher xylan conversion beneficial for diverse applications, such as bioethanol production. Thus, these agroindustrial by-products can be used within the framework of a circular economy, rendering an added value bioproduct, which is reused in the industry.

Xylooligosaccharides production from wheat middlings bioprocessed with Bacillus subtilis.

Prebiotic compounds are substrates selectively metabolized by beneficial gut microbiota causing a health-promoting effect. Despite some prebiotic carbohydrates have been largely studied, xylooligosaccharides (XOS) are important prebiotics derived from arabinoxylans, which are polysaccharides found in cereals. This study aimed to investigate the production of xylanolytic enzymes and XOS during bioprocessing of wheat middlings, a product derived from wheat flour production, using a probiotic Bacillus subtilis. The composition of XOS and the enzymatic and prebiotic activities of resulting B. subtilis cultures were evaluated. The activity of xylanolytic enzymes continuously enhanced during the 72 h bacterial growth, where β-xylosidase presented the highest value (70.31 U/mL). XOS profile and concentration varied considerably between control and bioprocessed samples and among these at different times. Maximum prebiotic activity score was found for the 24 h and 72 h bioprocessed samples (1.73 and 1.61, respectively) using the commercial probiotic Lactobacillus acidophilus LA-5. Wheat middlings showed to be a promising substrate for production of prebiotics like XOS and B. subtilis FTC01 appears to be a good source of xylanolytic enzymes.

Production of xylanolytic enzymes by Moesziomyces spp. using xylose, xylan and brewery’s spent grain as substrates

Xylanases play a crucial role in the hydrolysis of xylan-rich hemicelluloses and have wide industrial applications in the fuel, food, feed and pulp and paper industries. The production of these enzymes at low cost is of paramount importance for their commercial deployment. Moesziomyces antarcticus PYCC 5048T and M. aphidis PYCC 5535T were screened for their ability to produce xylanolytic enzymes when grown on d-xylose, xylan (beechwood) and brewery’s spent grain (BSG). The extracellular crude extracts produced were characterized and tested in xylan hydrolysis. The yeasts produced xylanolytic enzymes without cellulolytic activity on all the substrates tested. The highest xylanase volumetric activity was obtained with M. aphidis PYCC 5535T grown on BSG, reaching 518.2 U/ml, a value 8.4- and 4.7-fold higher than those achieved on xylan and d-xylose, respectively. The xylanase activities were characterized in relation to pH and temperature with optima at 4.5 and 50 °C, respectively. The extracts from both M. antarcticus PYCC 5048Tand M. aphidis PYCC 5535T were used in xylan hydrolysis, producing d-xylose as the major end product (0.43 and 0.34-0.47 gD-xylose/gxylan, respectively, at 50 °C) and relatively low or no xylobiose accumulation (from no detection to 0.12 gD-xylobiose/gxylan at 50 °C).

Production of xylanolitic enzymes and xylooligosaccharides by Aureobasidium pullulans CCT 1261 in submerged cultivation

Endo-β-1,4-xylanases are microbial-produced enzymes capable of converting lignocellulosic biomass in value-added products of biotechnological interest, such as xylooligosaccharides (XOS). Although endo-β-1,4-xylanase production using lignocellulosic substrates is commonly studied, there are few reports investigating the production of both xylanolytic enzymes and XOS by microbial species. In this paper, the production of xylanolytic enzymes and XOS by three Aureobasidium pullulans strains was evaluated during submerged cultivation, as well as the use of untreated and alkali pretreated agricultural substrates as sources of xylan for endo-β-1,4-xylanase production. The CCT 1261 strain showed the highest endo-β-1,4-xylanase activity (74.94 U/mL), specific activity (158.65 U/mg protein), productivity (P, 1.25 U/mL.h), maximum specific growth rate (μmax, 0.18 1/h), and maximum biomass concentration (Xmax, 4.10 g/L); and a low β-xylosidase production (0.19 U/mL). XOS production by the CCT 1261 strain was verified in the first 12 h of cultivation, which reached the total concentration of 1.68 mg/mL, and the XOS produced were comprised mainly of xylobiose and xylotriose. Among the agricultural substrates evaluated, untreated rice bran showed the highest amount of hemicellulose (29.6%) and a low lignin content (12.2%), which implied in the highest endo-β-1,4-xylanase activity (11.69 U/mL) when used as substrate in submerged cultivation. Endo-β-1,4-xylanase could be produced by A. pullulans in an economical way using a by-product of rice grain milling, which can be further improved by optimization of the submerged cultivation conditions.

An environment friendly and efficient process for xylitol bioconversion from enzymatic corncob hydrolysate by adapted Candida tropicalis

This study reported an environment friendly process for xylitol bioconversion from corncob hemicellulose hydrolysate prepared through xylanolytic enzymes by adapted Candida tropicalis. In order to improve the production of xylanolytic enzymes from Aspergillus terreus, the fermentation medium and growth conditions were optimized. Maximum xylanase (722U/g) and β-xylosidase (196U/g) production were exhibited on wheat bran and corncob (mass ratio of 7:3) medium supplemented with 2% (v/v) NaNO3 and 0.05% (v/v) Tween 80 at pH 6.8, 1:1 (v/w) moisture level, 20% inoculum level and 30°C for 120h of cultivation. For preparation of corncob hemicellulose hydrolysate, the optimum enzymatic hydrolysis conditions contained enzyme dosage (30.6U/g), water addition (19.2mL/g), temperature (48.01°C), pH (5.75). Under these conditions, the sugars of 18.03g/L xylose and 4.87g/L glucose were obtained in 8h. The corncob hemicellulose hydrolysate was used for xylitol fermentation and the maximum xylitol yield of 75.14% was obtained by adapted C. tropicalis after the optimization of fermentation.

Direct xylan conversion into glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma antarctica PYCC 5048T

Mannosylerythritol lipids (MEL) are glycolipid biosurfactants, produced by Pseudozyma spp., with increasing commercial interest. While MEL can be produced from d-glucose and d-xylose, the direct conversion of the respective lignocellulosic polysaccharides, cellulose and xylan, was not reported yet. The ability of Pseudozyma antarctica PYCC 5048T and Pseudozyma aphidis PYCC 5535T to use cellulose (Avicel®) and xylan (beechwood) as carbon and energy source has been assessed along with their capacity of producing cellulolytic and hemicellulolytic enzymes, toward a consolidated bioprocess (CBP) for MEL production. The yeasts assessed were neither able to grow in medium containing Avicel® nor produce cellulolytic enzymes under the conditions tested. On contrary, both yeasts were able to efficiently grow in xylan, but MEL production was only detected in P. antarctica PYCC 5048T cultures. MEL titers reached 1.3g/l after 10 days in batch cultures with 40g/l xylan, and 2.0g/l in fed-batch cultures with xylan feeding (additional 40g/l) at day 4. High levels of xylanase activities were detected in xylan cultures, reaching 47–62U/ml (31–32U/mg) at 50°C, and still exhibiting more than 10U/ml under physiological temperature (28°C). Total β-xylosidase activities, displayed mainly as wall-bounded and extracellular activity, accounted for 0.154 and 0.176U/ml in P. antarctica PYCC 5048T and P. aphidis PYCC 5535T cultures, respectively. The present results demonstrate the potential of Pseudozyma spp. for using directly a fraction of lignocellulosic biomass, xylan, and combining in the same bioprocess the production of xylanolytic enzymes with MEL production.

Partial Optimization of Endo-1, 4-Β-Xylanase Production by Aureobasidium pullulans Using Agro-Industrial Residues.

Objective(s) : Although bacteria and molds are the pioneering microorganisms for production of many enzymes, yet yeasts provide safe and reliable sources of enzymes with applications in food and feed. Single xylanase producer yeast was isolated from plant residues based on formation of transparent halo zones on xylan agar plates. The isolate showed much greater endo-1, 4-β-xylanase activity of 2.73 IU/ml after optimization of the initial extrinsic conditions. It was shown that the strain was also able to produce β-xylosidase (0.179 IU/ml) and α-arabinofuranosidase (0.063 IU/ml). Identification of the isolate was carried out and the endo-1, 4-β-xylanaseproduction by feeding the yeast cells on agro-industrial residues was optimized using one factor at a time approach. The enzyme producer strain was identified as Aureobasidiumpullulans. Based on the optimization approach, an incubation time of 48 hr at 27°C, inoculum size of 2% (v/v), initial pH value of 4 and agitation rate of 90 rpm were found to be the optimal conditions for achieving maximum yield of the enzyme. Xylan, containing agricultural residues, was evaluated as low-cost alternative carbon source for production of xylanolytic enzymes. The production of xylanase enzyme in media containing wheat bran as the sole carbon source was very similar to that of the medium containing pure beechwoodxylan. This finding indicates the feasibility of growing of A. pullulans strain SN090 on wheat bran as an alternate economical substrate in order for reducing the costs of enzyme production and using this fortified agro-industrial byproduct in formulation of animal feed.

Identification of a Novel Fungus, Leptosphaerulina chartarum SJTU59 and Characterization of Its Xylanolytic Enzymes

Xylanolytic enzymes are widely used in processing industries, e.g., pulp and paper, food, livestock feeds, and textile. Furthermore, certain xylanotic enzymes have demonstrated the capability to improve the resistance and immunity of plants. Screening of high-yield microbial xylanolytic enzyme producers is significant for improving large-scale cost-effective xylanolytic enzyme production. This study provided new evidence of high-level xylanolytic enzyme production by a novel fungus, designated Leptosphaerulina chartarum SJTU59. Under laboratory conditions, L. chartarum SJTU59 produced xylanolytic enzymes of up to 17.566 U/mL (i.e., 878.307 U/g substrate). The enzyme solution was relatively stable over a wide range of pH (pH 3.0 to pH 9.0) and temperature (40°C to 65°C) while showing high resistance to the majority of metal ions tested. Composition analysis of the hydrolytic products of xylan showed sufficient degradation by xylanolytic enzymes from L. chartarum SJTU59, mainly the monosaccharide xylose, and a small amount of xylobiose were enzymatically produced; whereas in the presence of sufficient xylan substrates, mainly xylooligosaccharides, an emerging prebiotic used in food industry, were produced. In addition, the xylanolytic enzyme preparation from L. chartarum SJTU59 could initiate tissue necrosis and oxidative burst in tobacco leaves, which may be related to enhanced plant defense to adversity and disease. L. chartarum SJTU59 possessed a complex xylanolytic enzyme system, from which two novel endo-β-1,4-xylanases of the glycoside hydrolase (GH) family 10, one novel endo-β-1,4-xylanase of the GH family 11, and one novel β-xylosidase of the GH family 43 were obtained via rapid amplification of complementary DNA ends. Given the high yield and stable properties of xylanolytic enzymes produced by L. chartarum SJTU59, future studies will be conducted to characterize the properties of individual xylanolytic enzymes from L. chartarum SJTU59. xylanolytic enzymes-encoding gene(s) of potential use for industrial and agricultural applications will be screened to construct genetically engineered strains.

Biomass hydrolyzing enzymes from plant pathogen Xanthomonas axonopodis pv. punicae: optimizing production and characterization

Xanthomonas axonopodis pv. punicae strain—a potent plant pathogen that causes blight disease in pomegranate—was screened for cellulolytic and xylanolytic enzyme production. This strain produced endo-β-1,4-glucanase, filter paper lyase activity (FPA), β-glucosidase and xylanase activities. Enzyme production was optimized with respect to major nutrient sources like carbon and nitrogen. Carboxy methyl cellulose (CMC) was a better inducer for FPA, CMCase and xylanase production, while starch was found to be best for cellobiase. Soybean meal/yeast extract at 0.5 % were better nitrogen sources for both cellulolytic and xylanolytic enzyme production while cellobiase and xylanase production was higher with peptone. Surfactants had no significant effect on levels of extracellular cellulases and xylanases. A temperature of 28 °C and pH 6–8 were optimum for production of enzyme activities. Growth under optimized conditions resulted in increases in different enzyme activities of around 1.72- to 5-fold. Physico-chemical characterization of enzymes showed that they were active over broad range of pH 4–8 with an optimum at 8. Cellulolytic enzymes showed a temperature optimum at around 55 °C while xylanase had highest activity at 45 °C. Heat treatment of enzyme extract at 75 °C for 1 h showed that xylanase activity was more stable than cellulolytic activities. Xanthomonas enzyme extracts were able to act on biologically pretreated paddy straw to release reducing sugars, and the amount of reducing sugars increased with incubation time. Thus, the enzymes produced by X. axonopodis pv. punicae are more versatile and resilient with respect to their activity at different pH and temperature. These enzymes can be overproduced and find application in different industries including food, pulp and paper and biorefineries for conversion of lignocellulosic biomass.

Isolation and properties of β-xylosidase from Aspergillus niger GS1 using corn pericarp upon solid state fermentation

There is growing interest in developing high-yield and low-cost production of xylanolytic enzymes for industrial applications using agroindustrial byproducts. A native strain of Aspergillus niger GS1 was used to produce β-xylosidase (EC 3.2.1.37) on solid state fermentation using corn pericarp (CP) with innovative alkaline electrolyzed water (AEW) pretreatment at room temperature. β-xylosidase was purified by ammonium sulfate fractionation followed by anion exchange and hydrophobic interaction chromatographies. β-Xylosidase showed a molecular weight of 111kDa, isoelectric point of 5.35 and specific activity of 386.7U (mg protein)−1, using p-nitrophenyl-β-d-xylopyranoside as substrate, at pH 5 and 60°C, and optimal activity at pH 4.5. Optimal temperature was 65°C, showing full activity after 1h at 60°C. Activity was reduced by 1mM β-mercaptoethanol (55.6±0.1%), and enhanced by 1mM SDS (11.0±0.03%). Km and Vmax were 6.1±0.9mM and 1364±105U (mgprotein)−1, respectively, whereas kcat was 5.1s−1. A predominant α-helix (41%) was determined from circular dichroism on β-xylosidase, while thermal transition profiles produced a Tm of 54.1±5.8°C, enthalpy change for unfolding of 67.4±6.7kJ/mol, and onset temperature of 37°C. Pre-treatment of CP using AEW is an ecologically friendly alternative to chemical and heat treatments for the production of relatively high levels of β-xylosidase.

Controlled Preparation of Cellulases with Xylanolytic Enzymes fromTrichoderma reesei(Hypocrea jecorina) by Continuous-Feed Cultivation Using Soluble Sugars

The objective of this study was to develop an efficient production system for cellulase preparation with a high level of xylanolytic enzymes using soluble carbon sources. When xylose and arabinose were simultaneously fed with glucose and cellobiose, a mutant of Trichoderma reesei, M3-1, showed sufficient levels of cellulolytic and xylanolytic activities, indicating that xylose and arabinose are good inducers for the production of xylanolytic enzymes. In a continuous feeding experiment using glucose/cellobiose and glucose/xylose/cellobiose, cellulase preparations with various levels of xylanolytic enzymes were obtained by altering the feeding solutions and the timing of their addition. The volumetric production rates for xylanolytic activities at the glucose/xylose/cellobiose-feeding phase were significantly higher than at the glucose/cellobiose-feeding phase, while those for cellulolytic activities were comparable under the two conditions. Thus the composition of the enzyme preparation produced by the mutant was readily controlled by varying the inducers and the pattern of their addition, facilitating the tailored production of enzymes in a diversity of bioconversion processes.

Production of xylanolytic enzymes by Aspergillus terricola in stirred tank and airlift tower loop bioreactors

Fungi producing high xylanase levels have attracted considerable attention because of their potential industrial applications. Batch cultivations of Aspergillus terricola fungus were evaluated in stirred tank and airlift bioreactors, by using wheat bran particles suspended in the cultivation medium as substrate for xylanase and β-xylosidase production. In the stirred tank bioreactor, in physical conditions of 30°C, 300 rpm, and aeration of 1 vvm (1 l min⁻¹), with direct inoculation of fungal spores, 7,475 U l⁻¹ xylanase was obtained after 36 h of operation, remaining constant after 24 h. In the absence of air injection in the stirred tank reactor, limited xylanase production was observed (final concentration 740 U l⁻¹). When the fermentation process was realized in the airlift bioreactor, xylanase production was higher than that observed in the stirred tank bioreactor, being 9,265 U l⁻¹ at 0.07 vvm (0.4 l min⁻¹) and 12,845 U l⁻¹ at 0.17 vvm (1 l min⁻¹) aeration rate.

Homologue expression of a β-xylosidase from native Aspergillus niger

Xylan constitutes the second most abundant source of renewable organic carbon on earth and is located in the cell walls of hardwood and softwood plants in the form of hemicellulose. Based on its availability, there is a growing interest in production of xylanolytic enzymes for industrial applications. β-1,4-xylan xylosidase (EC 3.2.1.37) hydrolyses from the nonreducing end of xylooligosaccharides arising from endo-1,4-β-xylanase activity. This work reports the partial characterization of a purified β-xylosidase from the native strain Aspergillus niger GS1 expressed by means of a fungal system. A gene encoding β-xylosidase, xlnD, was successfully cloned from a native A. niger GS1 strain. The recombinant enzyme was expressed in A. niger AB4.1 under control of A. nidulans gpdA promoter and trpC terminator. β-xylosidase was purified by affinity chromatography, with an apparent molecular weight of 90 kDa, and showed a maximum activity of 4,280 U mg protein(-1) at 70°C, pH 3.6. Half-life was 74 min at 70°C, activation energy was 58.9 kJ mol(-1), and at 50°C optimum stability was shown at pH 4.0-5.0. β-xylosidase kept residual activity >83% in the presence of dithiothreitol (DTT), β-mercaptoethanol, sodium dodecyl sulfate (SDS), ethylenediaminetetraacetate (EDTA), and Zn(2+). Production of a hemicellulolytic free xylosidase showed some advantages in applications, such as animal feed, enzymatic synthesis, and the fruit-juice industry where the presence of certain compounds, high temperatures, and acid media is unavoidable in the juice-making process.

Production of xylanolytic enzymes by Penicillium janczewskii

The production of extracellular xylanase, β-xylosidase and α- l-arabinofuranosidase by the mesophilic fungus Penicillium janczewskii under submerged cultivation was investigated with different carbon sources. Optimization steps included studies of carbon source concentration, temperature of cultivation and initial pH of culture medium. The production of these enzymes was increased two times when cultures were supplemented with brewer’s spent grain at 2% concentration, pH 6.0 and carried out at 25 °C. Under these optimized conditions were obtained xylanase activity of 15.19 U mL −1 and 23.54 U mg prot −1, β-xylosidase activity of 0.16 U mL −1 and 0.25 U mg prot −1 and α- l-arabinofuranosidase activity of 0.67 U mL −1 and 1.04 U mg prot −1. Brewer’s spent grain is a promising substrate for P. janczewskii growth and xylanolytic enzyme production, since it is the main by-product from the brewing industry, available in large amounts and at low-cost in many countries.

English

  Consortia of litter degrading fungal species were developed from different baiting substrates collected in and around Western ghat forest ecosystem, Coimbatore, Tamilnadu, India. Fifty-three litter degrading fungal species were isolated by nylon litterbag technique. The production of endo-b-1,4-xylanase (1,4-b-D-xylan xylanohydrolase, E.C. 3.2.1.8), b-D-xylosidase (1,4-b-xylan xylanohydrolase, E.C. 3.2.1.37) and protease was studied using oat spelt xylan as carbon source. Results showed that all fifty-three fungal species isolated from various litter samples produced fairly good xylanolytic enzyme activity. The xylanase and b-D-xylosidase activity ranges from 4.41 to 132.20 U and 48.72 to 1510.32 U, respectively. Growth was determined in terms of mycelial dry weight, which ranged between 0.209 and 1.047 mg/ml. The protease enzyme activity was from 19.7 to 60.8 U. This is the first report concerning xylanolytic enzyme production by the litter degrading fungi, isolated from litter samples.   Key words: Litter degrading fungi, xylanolytic enzyme, xylanase, b-xylosidase.

CreA mediates repression of the regulatory gene xlnR which controls the production of xylanolytic enzymes in Aspergillus nidulans

The Aspergillus nidulans xlnR gene encodes a Zn 2Cys 6 transcription activator necessary for the synthesis of the main xylanolytic enzymes, i.e. endo-xylanases X 22, X 24 and X 34, and β-xilosidase XlnD. Expression of xlnR is not sufficient for induction of genes encoding the xylanolytic complex, the presence of xylose is absolutely required. It has been established previously that the wide-domain carbon catabolite repressor CreA indirectly represses xlnA (encodes X 22) and xlnB (encodes X 24) genes as well as exerting direct repression on xlnA. This work provides evidence that CreA-mediated indirect repression occurs through repression of xlnR: (i) the xlnR gene promoter is repressed by glucose and this repression is abolished in creA d30 mutant strains and (ii) deregulated expression of xlnR completely relieves glucose repression of xlnA and xlnB. Thus, CreA and XlnR form a transcriptional cascade regulating A. nidulans xylanolytic genes.