Fermentative Enzymes Production Efficiency of Ethanologenic Bacteria Isolated from Raphia Palm Sap

Abstract

Background: Consolidated bioprocessing (CBP) candidate construction remains gray in the biotechnology of bioethanol production; and recent lead way involved genetic transformation of competent cells with ethanologenic and/or cellulolytic characteristics from natural microorganisms. Aim: As part of an ongoing study, the ethanologenic property of natural tropical bacteria population isolated from Raphia palm sap was investigated. Methods: Freshly tapped Raphia palm sap (PW) sample was obtained from a Raphia palm plantation site at Elemu Bus-stop, Jakande, Isolo, Lagos State, Nigeria. The morphological and biochemical characteristics (MBC) as well as 16s rDNA genotyping of the bacteria isolated from PW were used for identification. A representative α–keto acid decarboxylase (pyruvate decarboxylase -PDC) and alcohol dehydrogenase (ADH) productivities of the isolated bacteria in glucose supplemented media were determined by spectrophotometry. Results: The combination of MBC and 16s rDNA genotyping of the PW bacteria revealed about 6 isolates that were phylogenetically related to Bacillus pumilus, Bacillus subtilis, Paenibacillus validus, Macrococcus spp., Yokenella resenberghei; and Brevibacillus brevis. Meanwhile, efficient PDC productivity (0.5-1.8U/mL) was observed for Bacillus pumilus and Bacillus subtilis at pH 10.0, 25°C, 2.0g substrate concentration, NaNO3 as nitrogen source, and 72 hours incubation period. Bacillus pumilus and Bacillus subtilis efficiently produced ADH (0.5-2.0U/mL) optimally at pH 10.0, 25°C, 1.0g substrate concentration, peptone as nitrogen source, and 96 hours incubation period. Conclusion: The Raphia palm sap microbiota are efficiently ethanologenic. Thus, their genes can be adapted for genetic transformation in consolidated bioprocessing.