Biobleaching Of Paper Pulp Research Articles

Extremophilic Prokaryotic Endoxylanases: Diversity, Applicability, and Molecular Insights.

Extremophilic endoxylanases grabbed attention in recent years due to their applicability under harsh conditions of several industrial processes. Thermophilic, alkaliphilic, and acidophilic endoxylanases found their employability in bio-bleaching of paper pulp, bioconversion of lignocellulosic biomass into xylooligosaccharides, bioethanol production, and improving the nutritious value of bread and other bakery products. Xylanases obtained from extremophilic bacteria and archaea are considered better than fungal sources for several reasons. For example, enzymatic activity under broad pH and temperature range, low molecular weight, cellulase-free activity, and longer stability under extreme conditions of prokaryotic derived xylanases make them a good choice. In addition, a short life span, easy cultivation/harvesting methods, higher yield, and rapid DNA manipulations of bacterial and archaeal cells further reduces the overall cost of the product. This review focuses on the diversity of prokaryotic endoxylanases, their characteristics, and their functional attributes. Besides, the molecular mechanisms of their extreme behavior have also been presented here.

Recent developments of a co-immobilized laccase-mediator system: a review.

The laccase–mediator is a promising biocatalyst with many possible applications, including bioremediation, chemical synthesis, biobleaching of paper pulp, biosensing, textile finishing and wine stabilization. The immobilization of laccase and the mediator offers several improvements for laccase–mediator system applications because the storage and operational stabilities are frequently enhanced. Moreover, the reusability of the immobilized laccase and mediator represents a great advantage compared with the free laccase and mediator. In this work, we review the methods of co-immobilization of the laccase–mediator system for the first time systematically and comprehensively. In addition, we discuss the different methodologies of laccase and mediator immobilization that have been reported.

Potential of in situ SSF laccase produced from Ganoderma lucidum RCK 2011 in biobleaching of paper pulp.

Production of laccase from Ganoderma lucidum RCK 2011 under solid-state fermentation (SSF) conditions was optimized using response surface methodology, resulting in an approximate eightfold increase compared to that in the unoptimized media. Further, the enzyme produced under SSF as whole fermented substrate (in situ SSF laccase) was found to be more stable than the in vitro enzyme (harvested by downstreaming processing of fermented wheat bran). Interestingly, the biobleaching potentials of both in situ and in vitro SSF laccases were comparable, saving 25% chlorine dioxide for achieving similar pulp brightness as obtained in the pulp treated chemically. The reduction in the demand of chlorine dioxide in the pulp bleaching sequence subsequently decreased the levels of adsorbable organic halogen (AOX) in the resulting effluents of the process by 20% compared to the effluents obtained from chemical bleaching sequence. Therefore, direct application of in situ SSF laccase in pulp biobleaching will be environmentally friendly as well as economical and viable for implementation in paper mills.

Biobleaching of paper pulp with xylanase produced by Trichoderma asperellum.

This study is aimed at assessing the biobleaching activity of fungal xylanase on paper pulp isolated from Tirumala forest, Eastern Ghats of India. Of the 98 fungal isolates obtained after initial screening, eight isolates were selected and one potential strain was further cultivated under submerged fermentation for production of xylanase. The biobleaching efficiency on waste paper pulp and paper industry effluent was tested with crude enzyme. Xylanolytic activity by the chosen organism in submerged fermentation reached the maximum (981.1U ml-1) on the 5th day of incubation. Molecular characterisation of the isolate led to its identification as Trichoderma asperellum which exhibited the production of enzyme even at alkaline pH of the culture medium. Xylanase pretreatment of paper pulp had shown reduction in the Kappa number by 4.2 points and increased brightness by 4.0 points. FTIR and SEM studies revealed loosening of pulp fibres after enzyme treatment. In conclusion, xylanase of Trichoderma asperellum was effective as a pulp biobleaching agent and the process is economical as well as eco-friendly.

A Novel Multi-domain High Molecular, Salt-Stable Alkaline Xylanase from Alkalibacterium sp. SL3.

A novel multi-domain high molecular xylanase coding gene (xynSL3) was cloned from Alkalibacterium sp. SL3, an alkaliphilic bacterial strain isolated from the sediment of soda lake Dabusu. The deduced XynSL3 is composed of a putative signal peptide, three tandem domains of carbohydrate binding module (CBM) family 22, a catalytic domain of glycosyl hydrolase (GH) family 10 and a domain of CBM9. XynSL3 shares the highest identity of 66% to a hypothetical protein from Alkalibacterium sp. AK22 and has low identities (33–45%) with other functionally characterized xylanases. The gene xynSL3 was expressed heterologously in Escherichia coli and the recombinant enzyme demonstrated some particular characteristics. Purified recombinant XynSL3 (rXynSL3) was highly active and stable over the neutral and alkaline pH ranges from 7.0 to 12.0, with maximum activity at pH 9.0 and around 45% activity at pH 12.0. It had an apparent temperature optimum of 55°C and was stable at 50°C. The rXynSL3 was highly halotolerant, retaining more than 60% activity with 3 M NaCl and was stable at up to a 4 M concentration of NaCl. The hydrolysis products of rXynSL3 from corncob xylan were mainly xylobiose and xylotetraose. The activity of rXynSL3 was enhanced by Ca2+ and it has strong resistance to sodium dodecyl sulfate (SDS). This multi-domain, alkaline and salt-tolerant enzyme has great potential for basic research and industrial applications such as the biobleaching of paper pulp and production of xylo-oligosaccharides (XOS).

Xylanase: Applications in Biofuel Production

Background: Xylanase (EC 3.2.1.8, endo-1,4--xylan 4-xylanohydrolase) is a naturally occurring enzyme that breaks down hemicellulose by converting -1,4-xylan into xylooligosaccharides, xylobiose and xylose. It is frequently found in microbes and fungi. Considering the depleting resources of natural petroleum products especially petrol, current status of xylanase especially with respect to structural aspects and its application in biofuel production has been reviewed to show evidences that describe the significance of xylanase in bio-processing industry. Methods: The systematic investigation and web content related to xylanase and its industrial applications are reviewed. Results: Diverse primary studies and structured literature reviews met the review criteria. Studies comprised involvement of xylanase in various commercial applications. It has been reported to play an indispensable role in bio-bleaching of paper pulp, human digestion, baking industry, clarification of fruit juices and beer, malting and in the production of biofuels. Besides, structural aspects indicated importance of carbohydrate binding module in catalysis. Conclusion: The wide usage of xylanase from dough conditioning to biofuel production has garnered commercial importance to the enzyme. Many such explorations are anticipated in near future. Keywords: Animal feed, baking industry, bioethanol, biofuel, lignocellulosic biomass, paper and pulp industry, structural aspects, xylanase.

Know Your Chairman of Indian Academy of Microbiological Sciences

Ramesh Chander Kuhad, MSc, MPhil and PhD from Department of Microbiology, Bhopal University, Bhopal, India in 1980, 1981 and 1984, respectively. He started his career as an Assistant Professor in Department of Microbiology, Bhopal University, Bhopal in 1985. He moved on to University of Delhi South Campus as Assistant Professor in Microbiology. He has worked as a Senior Assistant Professor and an Associate Professor in Department of Microbiology, University of Delhi South Campus, New Delhi, India (1990–2003). In the year 2003, he was appointed as Professor and Chairman in Department of Biotechnology, Kurukshetra University, Kurukshetra, India and worked there for next 2 years (2003–2005) and established the department. In 2005, he came back as Professor to Department of Microbiology, University of Delhi South Campus, New Delhi, India, and headed the Department of Microbiology. He also served as Dean, Faculty of Inter-disciplinary and Applied Sciences (2005–2008), University of Delhi. Currently he is also serving as Joint Director, Institute of Life Long Learning, University of Delhi South Campus, New Delhi. He has also supervised more than 15 Research Projects, 13 PhD students and has published more than 125 papers in peer reviewed journals, majority of them are in International journals and 3 books. At present he is serving as an Associate Editor of Annals of Microbiology, Editor of Scientific reports (Nature Publishing Group), Journal of Sustainable Bioenergy Systems and Indian Journal of Microbiology. In addition he has also served as Guest Editor of the Special Issue of Biodegradation Journal. He has been the Member of Executive councils, Academic councils, Board of studies and Governing body of several Indian Universities/Colleges of University of Delhi. He has also been the Treasurer and General secretary (1997–2010) and President of Association of Microbiologists of India, AMI (2011) and recently he has been nominated by AMI as first Chairman of Indian Academy of Microbiological Sciences (2012). He has been the Recipient of Commonwealth Scholarship in the year 1985–1986, UNIDO/ICGEB Fellowship in 1994, Long-Term Overseas Research Associateship Award (Government of India) in 1995–1996 and Short-Term Biotechnology Overseas Associateship Award (Government of India) in 2002–2003. He was also the Organizing Chairman of the “49th Annual Conference of AMI and Internal Symposium on Microbial Biotechnology: Diversity, Genomics and Metagenomics” 18–20 Nov, 2008, Delhi, India. The main focus of his research is on Microbiology and Biotechnology of bioconversion of Lignocellulosic materials. In recent years, his main interests have been Bioethanol Production, Biotech-Animal Feed Development from Plant Biomass and Degumming of plant fiber and Biobleaching of Paper Pulp. Over all the main theme of his research is to make use of waste lignocellulosics and especially the crop byproducts.

Peculiarities of Pycnoporus species for applications in biotechnology

The genus Pycnoporus forms a cosmopolitan group of four species belonging to the polyporoid white-rot fungi, the most representative group of homobasidiomycetes causing wood decay. Pycnoporus fungi are listed as food- and cosmetic-grade microorganisms and emerged in the early 1990s as a genus whose biochemistry, biodegradation and biotechnological properties have since been progressively detailed. First highlighted for their original metabolic pathways involved in the functionalization of plant cell wall aromatic compounds to yield high-value molecules, e.g. aromas and antioxidants, the Pycnoporus species were later explored for their potential to produce various enzymes of industrial interest, such as hydrolases and oxidases. However, the most noteworthy feature of the genus Pycnoporus is its ability to overproduce high redox potential laccase-a multi-copper extracellular phenoloxidase-as the predominant ligninolytic enzyme. A major potential use of the Pycnoporus fungi is thus to harness their laccases for various applications such as the bioconversion of agricultural by-products and raw plant materials into valuable products, the biopulping and biobleaching of paper pulp and the biodegradation of organopollutants, xenobiotics and industrial contaminants. All the studies performed in the last decade show the genus Pycnoporus to be a strong contender for white biotechnology. In this review, we describe the properties of Pycnoporus fungi in relation to their biotechnological applications and potential.

New President of AMI—2011

Ramesh Chander Kuhad, male, microbiologist, M.Sc., M.Phil. and Ph.D. from Department of Microbiology, Bhopal University, Bhopal, India in 1980, 1981 and 1984, respectively. He started his career as an Assistant Professor in Department of Microbiology, Bhopal University, Bhopal in 1985. Then in the year 1988 he moved to University of Delhi South Campus as Assistant Professor in Microbiology. He has worked as a Senior Assistant Professor and an Associate Professor in Department of Microbiology, University of Delhi south Campus, New Delhi, India (1990–2003). In the year 2003, he was appointed as Professor and Chairman in Department of Biotechnology, Kurukshetra University, Kurukshetra, India and worked there for next 2 years (2003–2005) and established the department. In 2005, he came back as Professor to Department of Microbiology, University of Delhi South Campus, New Delhi, India, worked as Head, Department of Microbiology and also as Dean, Faculty of Inter-disciplinary and Applied Sciences (2005–2008). He has published more than 100 papers with SCI-934 (since 1996) and three books. In addition he has been the editor of Indian journal of Microbiology, published by Springer, since 2006 and recently he is serving as the Guest editor for the Special Issue of Biodegradation and 3 BIOTECH Journal. He has been the member of Executive council, Academic council and governing bodies of various Indian Universities and Colleges of University of Delhi. He has also served as Treasurer (9 years) and General Secretary (6 years) for Association of Microbiologists of India (AMI). Recently, he has been selected as President of The Association of Microbiologists of India for the year 2011. He has been the recipient of Commonwealth Scholarship in the year 1985–86, UNIDO/ICGEB Short-Term Fellowship in 1994, Long-Term Overseas Research Associateship Award (Govt. of India) in 1995–96 and Short-Term Biotechnology Overseas Associateship Award (Govt. of India) in 2002–03. He was also the Organizing Chairman of the 49th Annual Conference of AMI and International Symposium on Microbial Biotechnology: Diversity, Genomics and Metagenomics” 18–20 Nov, 2008. Delhi, India. The main focus of his research is on Microbiology and Biotechnology of Lignocellulose Bioconversion. In recent years, his main interests are Bioethanol production, Biotech-Animal feed development and Degumming & Biobleaching of paper pulp. Over all the main theme of his research is to make use of waste lignocellulosics and the crop byproducts in developing value added products.

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.

Molecular cloning and characterization of a novel metagenome-derived multicopper oxidase with alkaline laccase activity and highly soluble expression

Lac591, a gene encoding a novel multicopper oxidase with laccase activity, was identified through activity-based functional screening of a metagenomic library from mangrove soil. Sequence analysis revealed that lac591 encodes a protein of 500 amino acids with a predicted molecular mass of 57.4 kDa. Lac591 was overexpressed heterologously as soluble active enzyme in Escherichia coli and purified, giving rise to 380 mg of purified enzyme from 1 l induced culture, which is the highest expression report for bacterial laccase genes so far. Furthermore, the recombinant enzyme demonstrated activity toward classical laccase substrates syringaldazine (SGZ), guaiacol, and 2, 6-dimethoxyphenol (2, 6-DMP). The purified Lac591 exhibited maximal activity at 55 degrees C and pH 7.5 with guaiacol as substrate and was found to be stable in the pH range of 7.0-10.0. The substrate specificity on different substrates was studied with the purified enzyme, and the optimal substrates were in the order of 2, 6-DMP > catechol > alpha-naphthol > guaiacol > SGZ > 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid). The alkaline activity and highly soluble expression of Lac591 make it a good candidate of laccases in industrial applications for which classical laccases are unsuitable, such as biobleaching of paper pulp and dyestuffs processing.

Potential of solid-state fermentation enzymes of Aspergillus oryzae in biobleaching of paper pulp

Production of xylan-degrading enzymes, endo-β-xylanase (EC 3.2.1.8), β-xylosidase (EC 3.2.1.37), α- l-arabinofuranosidase (EC 3.2.1.55 and α-galactosidase (EC 3.2.1.22) by Aspergillus oryzae NRRL 1808 was investigated in solid-state fermentation using eucalyptus soda-anthraquinone and bagasse soda pulps as carbon feedstock. The impact of different nitrogen sources and initial fermentation pH on enzyme production was studied in medium optimisation experiments using fractional factorial design. The use of ammonium nitrate and corn steep liquor favoured xylanase production on eucalyptus pulp, whereas potassium nitrate and corn steep liquor increased xylanase yields on bagasse pulp. Xylanase production on eucalyptus and bagasse pulps under optimised conditions peaked on day 4 of cultivation (3200 and 2675 IU g −1 dry matter, respectively) which represents an increase in xylanase activity of 60% and 37%, respectively, over the non-opimised conditions. Biobleaching of eucalyptus and bagasse pulps was carried out using the whole fermented material (residual pulp, fungal biomass and in situ enzymes) from the cultivation of A. oryzae without a prior down streaming of the in situ enzymes from these pulps. Overall, the bagasse pulp was more susceptible to enzyme bleaching than eucalyptus pulp. In all instances, a greater brightness gain was induced with the in situ solid-state enzymes (0.9–3.0 points brightness increase) than a commercial enzyme control (0.8–2.5 points). At the same bleaching costs (US$ 1 or 3 t −1 pulp), the solid-state enzymes produced under optimised conditions were 20–36% more efficient in improving the brightness of paper pulp than the commercial enzyme. However, the presence of increased levels of side chain xylan degrading enzymes in the optimised medium did not improve the bleaching abilities of xylanase. It was demonstrated that bagasse pulp could successfully be used as carrier of A. oryzae enzymes in biobleaching of eucalyptus pulp without sacrificing the bleaching efficiency of xylanase.