Screening and identification of cellulase-producing bacteria and xylanase-producing bacteria from soil

Abstract

Screening of cellulase- and xylanase-producing bacteria from 40 and 45 soil samples, respectively and 10 biofertilizer samples, 51 bacterial strains were isolated (27 cellulase-producing and 24 xylanase producing strains). On the basis of their phenotypic and chemotaxonomic characteristics including phylogenetic analysis using 16S rRNA gene sequences, 7 strains were closed to Cohnella, 4 to Paenibacillus, 13 to Bacillus, 17 to Pseudomonas, 9 to Acinetobacter and 1 to Escherichia. The similarity of 16S rRNA gene sequence revealed that the cellulase-producing bacteria: PA4-1 (Group 1) was closely related to Cohnella thermotolerans CCUG 47242T (97.2%). PBS5 (Group 2), T3-3 (Group 3) and T3-2 (Group4) were closely related to Bacillus drentensis LMG 21831T (98.8%), B. megaterium IAM 13418T (88.0%) and B. cereus IAM 12605T (88.7%), respectively. N14-2 (Group 5) showed 93.0% similarity to Pseudomonas pseudoalcaligenes JCM 5968T. T6-4 (Group 6) showed 92.7% similarity to Pseudomonas nitroreducens DSM 14399T. The xylanase-producing bacteria: PT4-2 (Group 1) and PN12-3 (Group 3) showed 92.4 and 91.2% similarities to C. panacarvi KCTC 13060T, respectively. PN8-3 (Group 2) and PT6-2 (Group 4) showed 91.4 and 96.4% similarities to C. thermotolerans CCUG 47242T. PN13-1 (Group 5) and T3-2X (Group 6) showed 87.4 and 95.3% similarities to Paenibacillus agarexedens DSM 1327T. PT2-3 (Group 7) was closely related to Paenibacillus popilliae ATCC 14706T (91.8%). PN8-2 (Group 8) was closely related to B. subtilis KCTC 3135T (98.8%). PN1-2 (Group 9) was closely related to Pseudomonas aeruginosa MML 2212T (97.0%). PN9-3 (Group 10) showed 98.4% similarity to Acinetobacter baumannii ATCC 19606T. N9-2 (Group 11) was closely related to Escherichia coli KCTC 2441T (97.6%). Tested strains of Paenibacillus and Bacillus contained meso-diaminopimelic in cell wall peptidoglycan and had 7 isoprene units (MK-7) as predominant menaquinone. The DNA G+C contents of Cohnella strain were 52.3-64.9 mol%. In this study, Cohnella strain PA4-1, PT4-2, PN8-3, PN12-3 and PT6-2, Paenibacillus strain PN13-1, T3-2X and PT2-3, Bacillus strains PBS5 and T3-2, and Pseudomonas strain N14-2, T6-4 and PN1-2 were new species. However, DNA-DNA hybridization study were required to confirm their taxonomic position. Among 51 bacteria isolated, 27 cellulase-producing bacteria isolated produced cellulase 0-0.015 U/ml while the 24 xylanase-producing bacteria produced xylanase 0-0.48 U/ml. Strain PB11 produced highest endoglucanase. Optimal temperature and pH for endoglucanase activity were 60 °C, pH 7.5. Maximum endoglucanase activity was 0.11 U/ml, PA4-3 produced highest ß-glucosidase. Optimal temperature and pH for ß-glucosidase activity were 60 °C, pH 7.0. Maximum ß-glucosidase activity was 0.0091 U/ml. Optimal temperature and pH for xylanase activity were 65 °C, pH 8.0. Maximum xylanase activity was 0.51 U/ml.