Investigation of aerobic bacteria that isolated from Denizli Acigöl lake in terms of their productions of xylanases useable in paper industry

The effectiveness of xylanases as a prebleaching agent in pulp and paper industry has been established on a commercial scale. Especially, thermoalkalophilic and cellulase-free microbial xylanases are preferred in the pulp and paper industry. The strains from samples of alkaline and salty Acı Göl lake, were isolated by screening for xylanolysis on xylan agar media and then screened for cellulase hydrolysis on solid media containing carboxy methyl cellulose. Eight xylan hydrolyzing and not cellulose hydrolysis zone producing isolates were selected. The selected bacterial strains Ag1, Ag2, Ag8, Ag12, Ag13, Ag20 Ag32 and Ag35 were characterized and identified based on morphological, biochemical and physiological characters as belonging to the genus Bacillus.Optimum xylanase production temperatures evaluated as 400C for Ag1 and 350C for other seven isolates. Xylanase production of isolates in low-cost agriculture substrates, were also investigated. Maximum xylanase production of all isolates obtained by commercial birch wood xylan. Nevertheless, the xylanase productions by agriculture substrates were only negligible degree low, comparing the commercial xylan.Optimum xylanase activities determined as pH 9,0 at 350C and 600C at pH 9,0 for all eight isolates. Except isolate Ag1, crude culture filtrates of isolates were fully stable for one hour at 600C and pH 9.0. By the DNS method, low amounts of cellulase activity determined in the crude culture filtrates of Ag2, Ag8 and Ag35, the crude culture filtrates of isolates Ag12, Ag13, Ag20 and Ag32 did not show any detectable cellulase activity by the DNS method. Isolates Ag12, Ag13, Ag20 and Ag32 were selected for kraft pulp experiments to evaluate their efficiency in pulp bleaching. Xylanase pretreatment was carried out at pH 9.0, 60oC and 10 IU xylanase / g od-pulp conditions. In the Xylanase pretreatments, with crude culture filtrates of Ag12 and Ag13, equally 1,8 mg / od-pulp reducing sugar release obtained. And for Ag32 and Ag20, 2,7 and 3,6 mg / od-pulp educing sugar release obtained, resvectively. Xylanase-treated samples and un-enzyme treated control pulp were bleached with EDTA-peroxide bleaching sequence. After EDTA ( %1 ) treatment, pulps were chemically bleached at %1 NaOH, %2,5 H2O2, %5 pulp consistency and 70°C for 80 minutes. After chemical bleaching, comparing the control, 7.32, 5.98, 2.67 kappa number reduction obtained for isolates Ag32, Ag 12 and Ag20 respectively. The brightness of bleached pulps for isolates Ag32, Ag12 and Ag20 were 3.0, 1.0 and 5.0, respectively, and 1 % ISO higher than control pulp.