Microbial Diversity of Acetic Acid Producing Bacteria from Protein-Rich Residues

Background: Acetic acid bacteria (AAB) are concrete sets of organism which act as precursor for acetic acid production. Acetic acid is a colorless liquid with strong pungent and sour smell. It is synthesized from oxidation of ethanol by AAB. Vast studies have been made from sugary sources in the isolation of AAB.

Aim: The needs to study and utilize our protein-rich residues (PRR) for AAB presence spurn this study.

Place and Duration of Study: Department of Microbiology, University of Port Harcourt, between June and December 2018.

Methodology: The samples (beans, groundnut and powdered milk) used in this study were surface-sterilized, homogenized, pre-enriched (in balsam medium) and serially diluted with inoculum size (0.1ml) inoculated on sterilized glucose yeast peptone agar, Mannitol agar and low glycemic index (LGI) media and incubated at 30oC for 48 h using the spread plate technique. A total of 11 bacterial isolates were obtained and screened for acetic acid production in brain heart infusion and yeast glucose ethanol acetic acid broth at 30oC for 14 days and positive isolates were identified by titration method. AAB isolates with the highest acetic acid concentration were selected for molecular identification and further studies.

Results: Two Acetic acid bacteria identified in this study were Acetobacter and Gluconobacter. The result of this study indicated that Acetobacter had acetic acid concentration of 3.6g/100ml while Gluconobacter had 1.8g/100 ml. However, molecular identification highlighted Acetobacter as Bacillus cereus with Genbank accession number MK 332142; whereas Gluconobacter was Stenotrophomonas maltophilia MK 332143. The neighbor-joining phylogenetic tree and bioinformatics revealed B. cereus and S. maltophilia as 97% and 96% similarity index, 854 and 883 nucleotide sequencing letters as well as 450 and 410 base pairs.

Conclusion: This finding implied that “S. maltophilia” and “B. cereus” are predominant Acetic acid bacteria in spoilt beans and groundnut; and can act as potential strains with industrial importance to man and environment.