http://hdl.handle.net/2173/31415 Fri, 24 May 2013 08:57:44 GMT 2013-05-24T08:57:44Z http://hdl.handle.net/2173/31934 Title: Optimization of biobleaching of paper pulp in an expanded bed bioreactor with immobilized alkali stable xylanase by using response surface methodology Authors: Senthilkumar, Sundar R.; Dempsey, Michael J.; Krishnan, Chandraraj; Gunasekaran, Paramasamy Abstract: Purified alkali stable xylanase from Aspergillus fischeri was immobilized on polystyrene beads using diazotization method. An expanded bed bioreactor was developed with these immobilized beads to biobleach the paper pulp in continuous mode. Response surface methodology was applied to optimize the biobleaching conditions. Temperature (°C), flow rate of pulp (ml/min) and concentration of the pulp (%) were selected as variables in this study. Optimal conditions for biobleaching process were reaction temperature 60 °C, flow rate of 2 ml/min and 5% (w/v) of pulp. The kappa number reduced from 66 in the unbleached pulp to 20 (reduction of 87%). This system proves to be a better option for the conventional chlorine based pulp bleaching. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Bioresource technology, published by and copyright Elsevier. Sat, 01 Nov 2008 00:00:00 GMT http://hdl.handle.net/2173/31934 2008-11-01T00:00:00Z http://hdl.handle.net/2173/21152 Title: Particulate biofilm technology for wastewater treatment Authors: Dempsey, Michael J.; Boltz, Joshua P.; McQuarrie, James; Johnson, Barrie; Daigger, Glen T. Description: Presented at the IWA Biofilm Technologies Conference, 8-10 January 2008, Singapore. Wed, 09 Jan 2008 00:00:00 GMT http://hdl.handle.net/2173/21152 2008-01-09T00:00:00Z http://hdl.handle.net/2173/13319 Title: Thermal inactivation of alkali stable xylanases (XylA & XylB) from alkali tolerant fungus Aspergillus fischeri Fxn 1: effect of trehalose on their thermostability Authors: Rajan, Senthilkumar S.; Balasubramaniem, Ashokkumar; Krishnan, Chandraraj; Dempsey, Michael J.; Paramasamy, Gunasekaran Abstract: Alkali tolerant fungus Aspergillus fischeri Fxn 1 secretes two xylanases, an exoxylanase (XylA) and an endoxylanase (XylB) in solid state fermentation. Kinetic studies showed that thermal inactivation of purified XylA and XylB at pH 9, in the temperature ranging from 303K to 333K, followed first-order kinetics, with denaturation rate constants as 9.6 10-3 and 8.2 10-3 at 323K for XylA & XylB respectively. Heat-inactivation plots for purified enzymes were linear from which thermodynamic activation parameters, ΔH#, ΔS# and ΔG# have been estimated. The enzymatic activity was relatively stable with a respective half-life (t1/2) at 323K of 72 min for XylA and 84.5 min for XylB. The half life values of XylA & XylB increased to 169 and 136 min respectively, in the presence of 1 M trehalose. Separate tests at 60 C in the presence of additives (polyols, carbohydrates) showed that trehalose was the most effective stabiliser, which increased the stability of XylA & XylB to 64.7 & 17.63 % respectively. Description: Presented at Bioscience 2005 (Biochemical Society meeting), Glasgow, July 17-21, 2005. Tue, 19 Jul 2005 00:00:00 GMT http://hdl.handle.net/2173/13319 2005-07-19T00:00:00Z http://hdl.handle.net/2173/13330 Title: Natural immobilisation of microorganisms for continuous ethanol production Authors: Baptista, Cristina; Cóias, João M.A.; Oliveira, Ana C.M.; Oliveira, Nuno M.C.; Rocha, Jorge M.S.; Dempsey, Michael J.; Lannigan, Kevin C.; Benson, Paul S. Abstract: Using a growth medium based on cane blackstrap molasses, we compared ethanol production by two strains of Saccharomyces cerevisiae that were immobilized in polyurethane foam cubes in a fluidised-bed fermenter. One strain (NCYC 1119) was adhesive and extremely flocculent, whilst the other strain was not adhesive and only weakly flocculent. The strong flocs of NCYC 1119 caused blockage of the bed, so that stable operation could not be achieved beyond 15 days. Nevertheless, it was able to produce 40 g L−1 ethanol at a rate up to 16 g L−1 h−1 (D = 0.4 h−1), although this production period was limited to 192 h. In contrast, the non-adhesive strain was only capable of producing 28 g L−1 ethanol at a rate of 11 g L−1 h−1 at the same dilution rate, even though production continued for 576 h. Despite the conversion of sugars to ethanol not being complete during these trials (up to 47 g L−1 was expected), it was clearly demonstrated that the productivity of the adhesive strain was higher than that of the non-adhesive one. However, further work is required to develop this process into a robust, industrial system Description: This article was originally published following peer-review in Enzyme and Microbial Technology, published by and copyright Elsevier. Sun, 01 Jan 2006 00:00:00 GMT http://hdl.handle.net/2173/13330 2006-01-01T00:00:00Z