Dual application of agricultural residues for xylanase production and dye removal through solid state fermentation Prachi Kaushik * , Abhishek Mishra, Anushree Malik Applied Microbiology Laboratory, Centre for Rural Development and Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110 016, India article info Article history: Received 25 June 2014 Received in revised form 14 August 2014 Accepted 15 August 2014 Available online Keywords: Agro-residues Cellulase Dye removal Characterization Xylanase abstract The present study is a novel attempt to utilize agricultural residues for addressing the dual challenge faced by pulp and paper industries to control pollution caused due to pulp bleaching and release of colored waste water. Fungal isolate, Aspergillus lentulus, was utilized for the production of xylanase through solid state fermentation utilizing various low-cost agro-residues as substrate. Maximum xyla- nase production was obtained on the 4th day of incubation using wheat bran as the substrate (158.4 U/g) followed by corn cob (153.0 U/g), sugarcane bagasse (129.9 U/g) and wheat straw (49.4 U/g). These activities were accompanied by very low cellulase activities. The enzyme exhibited good stability at high pH and temperature (>75% activity retained at pH 9 and 70  C). Later, the left over spent fermented slurry was utilized to remove anionic (>85.0% removal) and cationic (>96.0% removal) dyes. Results indicate cellulase-free; pH and thermo stable nature of the xylanase enzyme which is required during bio- bleaching process. Moreover, successful utilization of spent residues from fermentation in dye removal process signify that the proposed technology can be utilized to meet the requirements of pulp and bleaching industries through an effective and sustainable approach. © 2014 Elsevier Ltd. All rights reserved. Introduction Pulp and paper industries have been considered as major polluting units across the world (Sumathi and Hung, 2006; Ratia et al., 2012). Different processes such as the pulp bleaching, deinking, production of colored paper etc. contribute to the pollu- tion caused by these industries. Last decade has seen an increase in the number of studies focusing on the possible pollution reduction, alternative waste treatment technologies, and waste management (Monte et al., 2009). Recently, utilization of microbial enzyme xylanase for pulp- bleaching has been intensely researched and adopted commer- cially (Polizeli et al., 2005). This results in cheaper and cleaner production process by avoiding the use of chlorine and significantly reducing the discharge of the pollutants. To make the enzyme application in industries more cost effective, its production using negative value substrates like agro-wastes has been recommended by many workers (Dhillon et al., 2011). Utilization of these agro- residues in bioprocesses has dual advantage of providing alterna- tive substrates as well as solving their disposal problems. Researchers have been utilizing sugarcane bagasse (Song and Wei, 2010), wheat bran (Garai and Kumar, 2013), coba husk (Fang et al., 2010), jatropha cake (Chaturvedi et al., 2010) etc. as the substrates for the production of enzymes through fermentation. Kraft pulping requires high temperatures and high pH and as most of the available xylanases are produced from mesophilic or- ganisms, they rapidly lose activity at temperatures above 50  C and at pH above 7. Currently efforts are being made to produce cellulase-free xylanases from thermophilic/thermotolerant micro- organisms which can retain their activity at alkaline pH and high temperatures (Collins et al., 2005; Nigam, 2013). Also, during xylanase production through solid state fermentation, after the extraction of enzyme, a lot of slurry comprising of degraded sub- strate and fungal biomass is produced which again has to be disposed off. If this spent slurry can be utilized for the dye removal process (another pollutant from paper industries) followed by composting of the dye laden slurry, a zero waste objective could be accomplished. Vermicomposting of such dye laden fermented slurry by Kaushik et al. (2013) have been successfully demonstrated where the end product could be used as a soil conditioner. Although economically and ecologically favourable, such in- tegrations have not been tested practically at a larger scale. The fungal isolate A. lentulus is an alkali, thermo and halo tolerant fungus (Kaushik and Malik, 2010) and has already been * Corresponding author. Tel.: þ91 11 26596011; fax: þ91 11 26591121. E-mail address: kaushik.prachi@yahoo.com (P. Kaushik). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2014.08.006 0964-8305/© 2014 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 96 (2014) 1e8