Morphological, Microscopic, Biochemical Characterization and Identification of Potential Isolated Acetic Acid Bacteria from the Pulp of Cola cordifolia Harvested in Northern Côte d'Ivoire

Abstract

Cola cordifolia is an under-exploited wild fruit from West Africa with high potential for microbial biotransformation processes. The present study aimed to isolate, characterise and select strains of acetic acid bacteria that could be used as starter cultures in vinegar production and other industrial fermentations. The physicochemical characteristics of the pulp (pH, moisture, dry matter, soluble dry extract, titratable acidity, vitamin C and alcohol content) were first determined. The acetic acid bacteria were then isolated, characterised using morphological and biochemical tests, and evaluated according to several technological criteria, notably their acidifying power, their tolerance to different concentrations of ethanol, glucose and acetic acid, and their tolerance to various temperatures and pH values. Their capacity to produce acetic acid in liquid medium was also determined. The results showed that the pulp of Cola cordifolia had favourable characteristics for the development of acetic bacteria, with a pH of 5.40 ± 0.04, a humidity of 71.33 ± 1.15% and a soluble dry extract of 15 °Brix. Forty-four presumptive isolates of acetic bacteria were obtained, of which eight showed a strong acidifying power and good tolerance to the main stress factors studied. The BAC4, BAC5, BAC11, BAC15 and BAC38 strains showed the highest acetic acid production, reaching up to 6.33 g/L. Multivariate analysis allowed the selection of four strains with the best technological performance. These results indicate that Cola cordifolia is a promising source of acetic acid bacteria that could be used as starter cultures for vinegar production and other biotechnological applications.