Isolation and Screening of Mannanase Producing Bacteria from Agricultural Wastes

Aim: The work focused on the isolation and screening of mannanase-producing bacteria associated with selected agricultural wastes.
Study Design: The first experiment, mannanase-producing bacteria were screened for mannanase production on Locust Bean Gum (LBG) agar medium and total bacterial count was determined. In the second experiment, the isolated bacteria were further screened for mannanase production in submerged state fermentation.
Place and Duration of Study: Microbiology Research Laboratory Federal University of Technology, Akure and Postgraduate Research Laboratory, Obafemi Awolowo University Ile-Ife, Nigeria between September 2011 and March 2012.
Methodology: The associated bacterial isolates were isolated on agar medium containing LBG and counted by standard microbiological methods. Quantitatively, mannanase production was conducted in mineral salt medium into which copra meal had been incorporated as the sole carbon source and enzyme activity was determined by dinitrosalicylic acid method.
Results: The highest bacteria counts were recorded in compost from wood dust with 5.5×1011 cfu/g, while cassava peels had the least of 1.02×106 cfu/g. In this study, 23 bacterial isolates showed positive results with clear zone around the cultures. Bacterial isolate 1A showed the highest ratio of clear zone to colony, while the lowest was observed in isolate 4B. In liquid broth, all the 23 isolates displayed mannanase activity between 0.28 to13.89 U/ml for static and 0.56 to13.43 U/ml for shaken condition, with the highest mannanase activity observed with isolate IA for both culture conditions. In the comparative study between static and shaken conditions, it was revealed that shaken cultures exhibited better yield than static cultures. According to the morphological and biochemical studies, the isolate 1A was primarily identified as the Klebsiella edwardsii.
Conclusion: In this investigation, bacterial isolates evaluated for mannanase production from agricultural wastes elaborated considerable mannanase activity and this could be applied in feed and prebiotic.