Assessment of Microbial Interactions between Potential Lactic Acid Bacteria Starters and Major Microorganisms During in vitro Fermentation in a Medium Similar to Cocoa Pulp in Côte d'Ivoire

Abstract

However, uncontrolled or random fermentations carried out in the country by farmers producing marketable cocoa beans of variable quality. The problem of variability in the quality of beans has led to significant economic losses in the country estimated at several billion CFA Francs. The objective of this work was to analyze the interactions between potential starter lactic acid bacteria and the major microorganisms selected during cocoa fermentations in Côte d’Ivoire. The work methodology began with the cultivation of yeast, lactic acid bacteria, acetic acid bacteria and Bacillus strains in their respective YPG, MRS, YEPG and BN media for 48 hours at 30°C. Then, the microbial load of each culture was determined and set at 105 cells/mL. The strains were subsequently placed in the similar interaction medium of cocoa pulp (PSM) alone (monoculture) or together (coculture) for the study of microbial interactions. This study took place over 5 days and samples were taken for analyzes after 0, 48 and 120 hours of incubation at 30°C. The interaction was monitored by assessing microbial growth using optical density and Thoma cell counts for monocultures and agar media for cocultures. Additionally, acid production and reduction in sugar intake were also measured over the 5 days. All crops showed good growth. Growth was greater in cocultures with values ​​ranging from 4.12 log (CFU/mL) to 9.21 log (CFU/mL). In addition, the cocktails acidified the environment much more than the monocultures with values ​​oscillating between 0.10 ± 0.00 and 0.21 ± 0.00. Also, the quantity of sugars in the different broths decreased significantly in the cocktails during the first 48 hours, going from 1.08 ± 0.08 to 0.20 ± 0.01. Microbial starters in monocultures and cocultures have shown their ability to adapt to the environment like cocoa pulp. The high microbial growth, sugar consumption, and acidification of the medium in the cocktails reflected a synergistic interaction between the strains during fermentation when they were together. In short, these strains could be used for a starter composition to control fermentation and obtain good quality beans.