Assessment of the Diversity of Lactic Acid Bacteria Involved in Cocoa Fermentation of Six Main Cocoa Producing Regions of Côte d’ivoire

Abstract

Aims: The variability of lactic acid bacteria (LAB) species involved in cocoa bean fermentation would cause inconsistency in the quality of cocoa. The aims of this study is to investigate the physicochemical parameters of cocoa bean fermentation in order to assess the activity and the molecular diversity of LAB involved in cocoa fermentation from six other regions of Côte d’Ivoire. Place and Duration of Study: Laboratory of Biotechnology, UFR Biosciences, University Félix Houphouet-Boigny (Côte d’Ivoire), between October 2016 and September 2017. Methodology: Spontaneous heap fermentations were conducted in six cocoa producing regions during 6 days. Physicochemical analysis of cocoa mass such as temperature, pH, titratable acidity and reducing sugars were carried out. In addition, LAB isolation was performed using plate culture on MRS medium and their fermentative type as well as their profile were determined. In addition, LAB species were determined by restriction profile analysis of the 16S gene. Results: a total of 568 LAB were isolated from cocoa fermentation. Biochemical and morphological identification of these germs revealed the clear dominance of the bacilli form (81.16%) and the heterofermentative type (over 80%) with facultative heterofermentative type recording more than half (54.4%) of the isolated population. Their molecular identification by sequencing the hypervariable zone of the 16S rDNA gene of a few representatives from each restriction group revealed 08 species with a predominance of Lactobacillus plantarum (76.76%) and Leuconostoc mesenteroides (15.31%) associated with minority species. This species diversity could be exploited for selecting appropriate starter cultures. Conclusion: This diversity of LAB species could be responsible for the variability of cocoa quality in Côte d’Ivoire.