Metagenomic analysis of Ghanaian cocoa beans fermentation and flavour formation
Theobroma cacao L. (cocoa) is a crop with major economic importance, and is grown by more than five million growers in more than 50 countries. More than 40 million people depend on cocoa production for their livelihood. In developing countries, microorganisms have played a vital and essential role in contributing to the improvement of the physiochemical, sensory and safety characteristics of the final products. The importance of bean fermentation in contributing to chocolate quality has been recognised for over 100 years. Chocolate acquires its colour and flavour during fermentation through the activities of a variety of microorganisms including yeasts, lactic acid bacteria, and acetic acid bacteria growing in the fermentation heap. Microorganisms can synthesize flavours as secondary metabolites during fermentation on nutrients such as sugars and amino acids. So far, all microbiological studies about cocoa bean fermentation were based on culture-dependent (isolation, cultivation, and identification), or, more recently, culture-independent (PCR-DGGE, or polymerase chain reaction denaturing gradient gel electrophoresis) methods. It is now generally accepted that the traditional microbiological culture-dependent methods are problematic, time-consuming, and in some cases, 99% of microorganisms are unculturable. The potential wealth of biological resources in fermentation microbes of cocoa are relatively untapped, unknown, and uncharacterized and specific microbes and genes encoding for specific flavour compounds are produced are also unknown. The aim of this research is to characterise microbial population and diversity using metagenomics and organic compounds present during Ghanaian cocoa beans fermentation and flavour formation. The pH, temperature and metabolites produced during fermentation will be measured as these have direct correlation on the fermentation process. The results are intended to provide information on which species of culturable and unculturable microbes are mostly involved in fermentation, genetic diversity among specific microorganism and also flavour compounds produced by each type of microbe and their population within the fermentation processes. It will also provide a great wealth of gene content, metabolic potential and the function of microbial communities. The microbes and enzymes identified can be engineered to enhance their activity for chocolate production and other biotechnological use.