Study about Acetic Acid Bacteria Isolated from Some Selected Waste Protein Source

Abstract

Background: Acetic acid bacteria (AAB) are an essential and diverse group of bacteria involved in producing fermented foods and beverages, primarily known for their production of acetic acid (ethanoic acid) used in the production of vinegar.
 Aim: This study aims to isolate Acetic Acid Bacteria from protein waste and quantify the acetic acid produced which will serve as a means of protein waste management/recycling to conserve the environment/society at large while producing the value-added product; acetic acid from waste protein sources (fish, milk, meat, egg, soy milk, beans and unpasteurized milk).
 Methodology: The samples were homogenized in sterile distilled water, followed by serial dilution and inoculation on glucose yeast calcium carbonate (GYC) agar using the spread plate method with an inoculum size of 0.1 ml. The plates were incubated at 30oC for 48 hours. Several biochemical tests, including oxidase, catalase, and Gram stain, were carried out on the isolates. The acetic acid production rate was estimated using the yeast glucose ethanol acetic acid (YGEA) medium. 
 Results: Twenty-five (25) (white, creamy and yellow pale-coloured) well-isolated colonies were selected to be analyzed. Out of 25 isolates, fourteen (14) suspected acetic acid bacteria because they produced clear zones around their colonies in the selective GYC culture medium. Of the 14 analyzed isolates, six (6) were Gram-negative rods. Presumptive identification of the acetic acid bacterial isolates includes Acetobacter aceti and Gluconobacter oxydans. Morphologically identified and biochemically confirmed acetic acid bacterial isolates were then further checked for their abilities to produce acetic acid by titration in YGEA (Yeast, Glucose, Ethanol, Acetic acid) medium. Acetic acid production rate varied among the isolates. Among three (3) acetic acid-producing strains, isolates from fish 2 showed the highest acetic acid production (24.34 g/100 ml) rate at 37oC, while those from milk 1 and meat 2 showed 23.96 g/100 ml and 23.46 g/100 ml, respectively.
 Conclusion: This study is based on the importance of AAB in converting low-value protein waste to value-added products such as acetic acid, ascorbic acid, cellulose and others. This is due to their ability to use protein waste as a substrate.