https://repositorium.sdum.uminho.pt/bitstream/1822/16854/1/3587.pdf

Bioactive phenolic compounds : production and extraction by solid-state fermentation. A review

Production and characterization of cellulolytic enzymes from the thermoacidophilic fungal Aspergillus terreus M11 under solid-state cultivation of corn stover

Xylanases are hydrolytic enzymes which cleave the β-1, 4 backbone of the complex plant cell wall polysaccharide xylan. Xylan is the major hemicellulosic constituent found in soft and hard food. It is the next most abundant renewable polysaccharide after cellulose. Xylanases and associated debranching enzymes produced by a variety of microorganisms including bacteria, actinomycetes, yeast and fungi bring hydrolysis of hemicelluloses. Despite thorough knowledge of microbial xylanolytic systems, further studies are required to achieve a complete understanding of the mechanism of xylan degradation by xylanases produced by microorganisms and their promising use in pulp biobleaching. Cellulase-free xylanases are important in pulp biobleaching as alternatives to the use of toxic chlorinated compounds because of the environmental hazards and diseases caused by the release of the adsorbable organic halogens. In this review, we have focused on the studies of structural composition of xylan in plants, their classification, sources of xylanases, extremophilic xylanases, modes of fermentation for the production of xylanases, factors affecting xylanase production, statistical approaches such as Plackett Burman, Response Surface Methodology to enhance xylanase production, purification, characterization, molecular cloning and expression. Besides this, review has focused on the microbial enzyme complex involved in the complete breakdown of xylan and the studies on xylanase regulation and their potential industrial applications with special reference to pulp biobleaching, which is directly related to increasing pulp brightness and reduction in environmental pollution.

/pdf/microbial-xylanases-and-their-industrial-application-in-pulp-oanprfzwyh.pdf

Microbial xylanases and their industrial application in pulp and paper biobleaching: a review.

Optimization of media composition for Nattokinase production by Bacillus subtilis using response surface methodology.

High-level of xylanase production by the thermophilic Paecilomyces themophila J18 on wheat straw in solid-state fermentation

Optimization of medium composition for alkali-stable xylanase production by Aspergillus fischeri Fxn 1 in solid-state fermentation using central composite rotary design

Optimization of biobleaching of paper pulp in an expanded bed bioreactor with immobilized alkali stable xylanase by using response surface methodology.

Aspergillus niger NRRL330 produces extracellular beta-fructofuranosidase (Ffase), and its production is subject to repression by hexoses in the medium. After ultraviolet mutagenization and selection, seven derepressed mutants resistant to 2-deoxyglucose (2-DG) were isolated on Czapek's minimal medium containing glycerol. One of the mutants, designated DGRA-1, produced higher levels of Ffase. A considerable difference occurred in the mutants with reference to hexokinase and intracellular acid phosphatase activities. The hexokinase activity of the mutant DGRA-1 (0.69 U/mg) was 1.8-fold higher than the wild type (0.38 U/mg). Intracellular acid phosphatase activity of the mutant DGRA-1 (0.83 U/g of mycelia) was twofold higher than that of the wild type (0.42 U/g of mycelia), suggesting that phosphorylation and dephosphorylation steps could attribute to the 2-DG resistance of A. niger. However, additional mutations could account for the increased production of Ffase in the mutant DGRA-1.

Derepressed 2-deoxyglucose-resistant mutants of Aspergillus niger with altered hexokinase and acid phosphatase activity in hyperproduction of beta-fructofuranosidase.

A low molecular weight, alkaline-stable endoxylanase (XylB) was purified to homogeneity from solid-state culture of Aspergillus fischeri Fxn1. XylB had a molecular mass of 13 kDa which is the lowest of reported xylanases. Optimal activity was at pH 6 and 55 °C. XylB was stable from pH 4.5 to 10 and up to 60 °C. It was non-glycosylated. The apparent K
m and V
max values of XylB on birch wood xylan were 0.53 mg ml−1 and 0.2 mmol min−1 mg−1, respectively. The activity of XylB was not inhibited by Cd2+, Zn2+, Co2+, EDTA, iodoacetamide, β-mercaptoethanol and acetic anhydride but strongly inhibited by 10 mm of N-bromosuccinimide, Hg2+, Pb2+ and p-hydroxymercuric benzoate. XylB is an endoxylanase since it hydrolysed xylan resulting the formation of xylo-oligomers but not of xylose residues.

Sundar Rajan Senthilkumar

Papers

Optimization of medium composition for alkali-stable xylanase production by Aspergillus fischeri Fxn 1 in solid-state fermentation using central composite rotary design

Optimization of biobleaching of paper pulp in an expanded bed bioreactor with immobilized alkali stable xylanase by using response surface methodology.

Derepressed 2-deoxyglucose-resistant mutants of Aspergillus niger with altered hexokinase and acid phosphatase activity in hyperproduction of beta-fructofuranosidase.

Purification and characterization of a low molecular weight endoxylanase from solid-state cultures of alkali-tolerant Aspergillus fischeri.