SCREENING OF XYLANASE PRODUCING MICROORGANISMS PUBLISHEDA. BURLACU, C.P. CORNEA, F. ISRAEL-ROMING
Abstract: Hemicellulose, the second most abundant natural polymer on earth, is a mixture of polysaccharides and vegetable gums, found, together with cellulose and lignin, in plant cell walls. Xylanases are enzymes involved in the hydrolysis of xylan, the major component of hemicellulose. These enzymes are able to hydrolyze xylan, by breaking the β-1,4-glycoside linkages, in order to produce xylose and other degradation compounds. Many degrading microorganisms such as fungi, bacteria, yeast etc. have been found to produce xylanases. In this study, our aim was to test different strains regarding their ability to produce xylanases. A screening of the bacterial and fungal strains was performed in order to select the microorganisms that could produce higher amount of xylanases. The strains were cultivated on minimal agar medium with 0.5% oat spelt xylan as the carbon source. The plates were incubated at 28ºC, for three to ten days (depending on microorganism) and analyzed at every 24 hours for the occurrence and evaluation of the halo diameter, using Congo red staining. Based on the xylan hydrolysis area, several microbial strains were selected for further analysis: Bacillus amyloliquefaciens B4, B.amyloliquefaciens BN7, Aspergillus flavus T11, A. flavus AFR A. niger prot., A.niger An4, A.brasiliensis, Trichoderma atroviride TK20, T.viride UV, T. viride Tv2 T.harzianum TK25, T. harzianum P8, Fusarium sp., Penicillium digitatum, Rhizoctonia solani, P. verruculosum KUCC 47345. For enzymatic analysis and the pH variation, the microorganisms were cultivated in liquid medium containing 0.5% oat spelt xylan, at 28ºC for 5-9 days. In addition, the protein assay was carried out in order to calculate the specific enzymatic activity. The best activities were detected in B.amyloliquefaciens B4, A. brasiliensis ATCC 16404, Penicillium digitatum and A.niger An4. These results are significant for further studies regarding lignocellulosic biomass biodegradation by an enzymatic complex.
Keywords: Xylanase, Bacillus, Aspergillus, Trichoderma, Fusarium, Penicillium