Optimization of xylanase production by Thermomyces lanuginosus in solid state fermentation

A Comprehensive Review on Valorization of Agro-Food Industrial Residues by Solid-State Fermentation

Agro-food industrial residues (AFIRs) are generated in large quantities all over the world. The vast majority of these wastes are lignocellulosic wastes that are a source of value-added products. Technologies such as solid-state fermentation (SSF) for bioconversion of lignocellulosic waste, based on the production of a wide range of bioproducts, offer both economic and environmental benefits. The versatility of application and interest in applying the principles of the circular bioeconomy make SSF one of the valorization strategies for AFIRs that can have a significant impact on the environment of the wider community. Important criteria for SSF are the selection of the appropriate and compatible substrate and microorganism, as well as the selection of the optimal process parameters for the growth of the microorganism and the production of the desired metabolites. This review provides an overview of the management of AFIRs by SSF: the current application, classification, and chemical composition of AFIRs; the catalytic function and potential application of enzymes produced by various microorganisms during SSF cultivation on AFIRs; the production of phenolic compounds by SSF; and a brief insight into the role of SSF treatment of AFIRs for feed improvement and biofuel production.

Effect of Oligosaccharide Degree of Polymerization on the Induction of Xylan-Degrading Enzymes by Fusarium oxysporum f. sp. Lycopersici

Xylan is one of the most abundant carbohydrates on Earth. Complete degradation of xylan is achieved by the collaborative action of endo-β-1,4-xylanases and β-d-xylosidases and a number of accessories enzymes. In filamentous fungi, the xylanolytic system is controlled through induction and repression. However, the exact mechanism remains unclear. Substrates containing xylan promote the induction of xylanases, which release xylooligosaccharides. These, in turn, induce expression of xylanase-encoding genes. Here, we aimed to determine which xylan degradation products acted as inducers, and whether the size of the released oligomer correlated with its induction strength. To this end, we compared xylanase production by different inducers, such as sophorose, lactose, cellooligosaccharides, and xylooligosaccharides in Fusarium oxysporum f. sp. lycopersici. Results indicate that xylooligosaccharides are more effective than other substrates at inducing endoxylanase and β-xylosidases. Moreover, we report a correlation between the degree of xylooligosaccharide polymerization and induction efficiency of each enzyme. Specifically, xylotetraose is the best inducer of endoxylanase, xylohexaose of extracellular β-xylosidase, and xylobiose of cell-bound β-xylosidase.

Xylanase production from Thermomyces lanuginosus VAPS-24 using low cost agro-industrial residues via hybrid optimization tools and its potential use for saccharification

The xylanase production from Thermomyces lanuginosus VAPS-24 has been optimized using OFAT (One factor at a time) approach using agro-industrial substrates. Further, central composite design (CCD) has been employed to optimize various process parameters such as temperature (45-55°C), carbon source concentration (1.5-2.5%), fermentation time (72-120h) and production medium pH (6-8). Maximum xylanase yield after RSM optimization was approximately double (119.91±2.53UmL^-1) than un-optimized conditions (61.09±0.91UmL^-1). Several hybrid statistical tools such as Genetic Algorithm-Response Surface Methodology (GA-RSM), Artificial Neural Network (ANN), Genetic Algorithm-Artificial Neural Network (GA-ANN) were employed to obtain more optimized process parameters to maximize the xylanase production and observed an increase of 10.50% xylanase production (132.51±3.27UmL^-1) as compared to RSM response (119.91±2.53UmL^-1). The various pretreated and untreated agricultural residues were subjected to saccharification by using crude xylanase in which the pretreated rice straw yielded maximum fermentable sugars 126.89mgg^-1.

Experimental design of response surface methodology used for utilisation of palm kernel cake as solid substrate for optimised production of fungal mannanase

The results obtained from this work strongly indicate that the solid state fermentation (SSF) system using the palm kernel cake (PKC) as a substrate is an economical method for the production of β-mannanase at extremely low operational cost based on the fact that PKC is one of the cheap and abundant agro-waste by-products of the palm oil industry. Under initial conditions, i.e. 2 mm particle size of PKC, the moisture ratio of 1:1 of PKC:moistening agent and pH 7, Malbranchea cinnamomea NFCCI 3724 produced 109 U/gram distribution of the substrate (gds). The production of β-mannanase was optimised by the statistical approach response surface methodology (RSM) using independent variables, namely initial moisture (12.5), pH (9.0) and solka floc (100 mg). Noticeably, six fold enhancement of β-mannanase production (599 U/gds) was obtained under statistically optimised conditions. HPLC results revealed that β-mannanase is an endo-active enzyme that generated manno-oligosaccharides with a degree of polymerisation (DP) of 3 and 4. Semi-native PAGE analysis revealed that M. cinnamomea produced three isoforms of mannanase. Selective production of oligosaccharide makes M. cinnamomea β-mannanase an attractive enzyme for use in food and nutraceutical industries.

Validation of an Analytical Method for the Determination of the Activity of Xylanase in Animal Feed Additives and in Animal Feedingstuffs

Exogenous carbohydrases are commonly added to monogastric feed to help degrade non-starch polysaccharides (NSP). This action can increase the nutrient availability of feedingstuffs and decrease digestive disturbances, thus improving animal performance. This in turn can lead to improved feed conversion efficiency in meat and egg production. In light of the benefits associated with dietary xylanase inclusion, so too has it become increasingly relevant to quantity them in poultry feed premixtures with additional enzyme activities and directly in compound feed. Hitherto, the analysis of the activity of xylanase in animal feeds has proved difficult. Despite the widespread acceptance of the DNS method for the quantification of xylanase activity, it is not without limitations which can lead to erroneous under- or over-estimation of activity, and is particularly variable depending on the feed matrix wherein it is measured. The current method validation examined the following parameters: linearity, precision, uncertainty, sensitivity (limit of detection and limit of quantification) and the experiments were designed to highlight any interference from protease co-ingredients and possible matrix effects in various types of supplemented feed. The assay method described is convenient and inexpensive and could be applied to the rapid and routine analysis of xylanases in animal feeds during quality control and in investigating fraudulent adulteration of feed to ensure the authenticity and traceability of the product.

Production and characterization of acidophilic xylanolytic enzymes from Penicillium oxalicum GZ-2

Multiple acidophilic xylanolytic enzymes were produced by Penicillium oxalicum GZ-2 during growth on wheat straw, rice straw, corn stover, and wheat bran. The expression of xylanase isoforms was dependent on substrate type and nitrogen source. The zymograms produced by the SDS-PAGE resolution of the crude enzymes indicated that wheat straw was the best inducer, resulting in the highest xylanase (115.2U/mL) and β-xylosidase (89mU/mL) activities during submerged fermentation. The optimum temperature and pH for xylanase activity were 50°C and 4.0, respectively; however, the crude xylanase enzymes exhibited remarkable stability over a broad pH range and showed more than 90% activity at 50°C for 30min at pH 4.0-8.0. The results revealed that P. oxalicum GZ-2 is a promising acidophilic xylanase-producing microorganism that has great potential to be used in biofuels, animal feed, and food industry applications.

Production of a xylose-stimulated β-glucosidase and a cellulase-free thermostable xylanase by the thermophilic fungus Humicola brevis var. thermoidea under solid state fermentation

Humicola brevis var. thermoidea cultivated under solid state fermentation in wheat bran and water (1:2 w/v) was a good producer of β-glucosidase and xylanase. After optimization using response surface methodology the level of xylanase reached 5,791.2 ± 411.2 U g(-1), while β-glucosidase production was increased about 2.6-fold, reaching 20.7 ± 1.5 U g(-1). Cellulase levels were negligible. Biochemical characterization of H. brevis β-glucosidase and xylanase activities showed that they were stable in a wide pH range. Optimum pH for β-glucosidase and xylanase activities were 5.0 and 5.5, respectively, but the xylanase showed 80 % of maximal activity when assayed at pH 8.0. Both enzymes presented high thermal stability. The β-glucosidase maintained about 95 % of its activity after 26 h in water at 55 °C, with half-lives of 15.7 h at 60 °C and 5.1 h at 65 °C. The presence of xylose during heat treatment at 65 °C protected β-glucosidase against thermal inactivation. Xylanase maintained about 80 % of its activity after 200 h in water at 60 °C. Xylose stimulated β-glucosidase activity up to 1.7-fold, at 200 mmol L(-1). The notable features of both xylanase and β-glucosidase suggest that H. brevis crude culture extract may be useful to compose efficient enzymatic cocktails for lignocellulosic materials treatment or paper pulp biobleaching.

Utilization of deoiled Jatropha curcas seed cake for production of xylanase from thermophilic Scytalidium thermophilum

Jatropha curcas is a major biodiesel crop. Large amount of deoiled cake is generated as by-product during biodiesel production from its seeds. Deoiled J. curcas seed cake was assessed as substrate for the production of xylanase from thermophilic fungus Scytalidium thermophilum by solid-state fermentation. The seed cake was efficiently utilized by S. thermophilum for its growth during which it produced good amount of heat stable extracellular xylanase. The solid-state fermentation conditions were optimized for maximum xylanase production. Under the optimized conditions viz. deoiled seed cake supplemented with 1% oat-spelt xylan, adjusted to pH 9.0, moisture content 1:3 w/v, inoculated with 1×10(6) spores per 5 g cake and incubated at 45 °C, 1455 U xylanase/g deoiled seed cake was obtained. The xylanase was useful in biobleaching of paper pulp. Solid-state fermentation of deoiled cake appears a potentially viable approach for its effective utilization.