Influence of environmental microbiota on the activity and metabolism of starter cultures used in coffee beans fermentation

Abstract

Coffee is currently one of the largest commodity in market value in the world, grown in more than 70 countries. The ripe fruits of coffee harbor several microorganisms, including bacteria, yeasts and filamentous fungi. During the wet processing of coffee postharvest, the fruits are pulped and the beans are submitted to the fermentation process for removal of the mucilage adhered to the parchment. This fermentation is done in an uncontrolled manner and can be spontaneous or by the use of starter cultures. This study aimed to evaluate the influence of the environmental microbiota on the metabolic activity of starter culture used to control the fermentation process in an experimental farm located in the cerrado region of Minas Gerais, Patrocínio. The following environmental samples were collected: soil, leaves, whole fruits, pulped and washing water. Then fermentation using the starter culture Pediococcus acidilactici LPBC161 and Pichia fermentans YC5.2 was conducted for 24 hours. Samples of the liquid fraction of fermentation and grains were sampled at 0, 9, 18 and 24 hours. The microbiomes of all samples were analyzed by new generation sequencing through the Illumina platform. The metabolism of the starter culture were analyzed by chromatographic techniques in the fermentation samples. The ambient microbiota was dominated by Enterobacteriaceae and Saccharomycetales. After the fermentation process, Pichia and the Lactobacillaceae family (which includes P. acidilactici) represented more than 70% of the total microbial community. The positive interaction between the starter cultures resulted in the formation of primary metabolites (such as ethanol and lactic acid) and important aroma impacting compounds (ethyl acetate, isoamyl acetate and ethyl isobutyrate). Through the data generated, it is expected that these results will help coffee producers in Brazil to better control the fermentation stage and, consequently, bring improvement in the quality of coffee produced in the country.