Isolation and characterization of Microorganisms involved in the Wet-Process coffee production: Impact on coffee qualities

Thai coffee farmers/producers prefer wet-processed coffee production process relying on natural microorganisms present on coffee beans which often leads to inconsistent coffee qualities as several factors such as climate, farmers’ practices, and natural microorganism diversity vary uncontrollably. This study aimed at isolating and characterizing the microorganisms significantly influencing coffee quality in the wet-processed coffee production. Samples were collected from the Royal Project Development Center at Tien Tok and Narit Coffee Farm at the Inthanon Royal Agricultural Station, significant area for growing and Arabica coffee processing. Lactic Acid Bacteria was isolated using MRS agar supplemented with 0.12 g/L bromocresol purple and 0.2 g/L sodium azide under 25°C incubation while PDA agar containing 100 mg/L ampicillin was employed for yeasts. All isolated microorganisms were identified via Next Generation Sequencing techniques and organic acids were analyzed via High Performance Liquid chromatography. Isolated microorganisms included 6 bacteria (i.e., Weissella cibaria,) and 2 yeasts (e.g., Pichia fermentans). Coffee beans fermented with L. plantarum and W. cibaria produced lactic acid, acidity and freshness enhancer of coffee, at 18.11 and 8.67 g/L, respectively, leading to, respectively, 80.81 and 83.13 cupping scores while those fermented with P. fermentans known for esters producing capability led to 83.58 cupping score given that naturally fermented coffee bean (control) was of 81.96 cupping scores. It appeared that microorganisms played a significant role on coffee quality during wet-processed fermentation. Therefore, inoculation of few carefully selected microorganisms may enhance the quality of wet-processed coffee and leads to developing new techniques for producing higher-quality coffee.