Biotransformation of Unsold Mangoes and Cashew Apples by Acetic Acid Bacteria Isolated from Fermented Beverages

Abstract

Aims: The recovery of agricultural waste is regarded as a strategy for reducing its environmental impact while generating high value-added products. Thus, this study aimed to evaluate the potential of acetic acid bacteria isolated from fermented beverages to biotransform unsold mangoes and cashew apples for their valorisation through the production of organic acids. Methodology: For this purpose, the technological properties of Acetobacter pasteurianus and Acetobacter oryzoeni strains isolated from traditional beverages (tchapalo and palm wine) were evaluated by assessing their growth at different temperatures (30, 37, and 44°C) and ethanol concentrations (2, 4, 6, 8, 10, 15, and 20%, v/v). Furthermore, the ability of these acetic acid bacteria to acidify cashew apple juice (the pseudofruit of Anacardium occidentale L.) and mango juice (Mangifera indica cv. Kent) was investigated in the presence and absence of ethanol. Results: The results showed that Acetobacter pasteurianus and Acetobacter oryzoeni exhibited optimal growth at 30°C and 37°C. Organic acid production was higher at 37°C, where titratable acidity increased from 0.42 to 0.96% for A. pasteurianus and from 0.33 to 1.13% for A. oryzoeni. Ethanol concentrations of 4% and 6% promoted substantial organic acid production. In fermented juices without ethanol supplementation, titratable acidity was higher in cashew apple juice than in mango juice. However, in the presence of ethanol, titratable acidity was higher in mango juice. Conclusion: A. pasteurianus and A. oryzoeni demonstrated strong technological potential for the biotransformation of mango and cashew apple juices. The findings suggest that cashew apple juice may preferentially support gluconic acid production, whereas mango juice may be more favourable for acetic acid production by acetic acid bacteria. However, these interpretations are based on indirect physicochemical indicators (pH, titratable acidity, and total soluble solids), and further studies involving direct quantification of organic acids are needed to confirm the metabolic pathways involved.