The microbiology of arabica and robusta coffee cherries: a comparative study of indigenous bacteria with presumptive impact on coffee quality.

Arabica and robusta are the two major coffee beans being sold worldwide. It is well recognized that coffee quality is influenced by their origin and the microbiological activities that drive their fermentation. However, in many coffee plantations, information about the natural diversity of bacteria that inhabit the arabica and robusta coffee cherries is limited. Here, we sampled arabica and robusta coffee cherries from Malang, East Java, Indonesia, then sequenced and analysed their bacterial composition. We found that: (a) arabica cherries contained bacteria with less diversity and abundance compared with robusta; (b) both coffee cherries were heavily populated by extremophiles, presumably dispersed from volcanic activities; (c) groups known to be involved in coffee fermentation such as lactic acid bacteria, acetic acid bacteria, Enterobacteria, and soil-associated bacteria were present in both arabica and robusta coffee cherries, and (d) arabica cherries were dominated by Leuconostoc pseudomesenteroides. These findings highlight that coffee cherry bacteria are highly diverse, the majority of which might come from the environment, with some potentially beneficial or detrimental to coffee quality. Knowledge of the natural microbial diversity of coffee cherries may be useful for the development of coffee fermentation technologies to yield coffee beans with consistent quality.

Ethanol Production from Oil Palm Trunk: A Combined Strategy Using an Effective Pretreatment and Simultaneous Saccharification and Cofermentation.

BACKGROUND: Oil palm trunk (OPT) with highly cellulose content is a valuable bioresource for bioethanol production. To produce ethanol from biomass, pretreatment is an essential step in the conversion of lignocellulosic biomass to fermentable sugars such as glucose and xylose. Several pretreatment methods have been developed to overcome biomass recalcitrance. In this study, the effects of different pretreatment methods such as alkali pretreatment, microwave-alkali, and alkaline peroxide combined with autoclave on the lignocellulosic biomass structure were investigated. Moreover, ethanol production from the treated biomass was performed by simultaneous saccharification and cofermentation (SSCF) under different temperatures, fermentation times, and cell ratios of Saccharomyces cerevisiae NCYC 479 and pentose-utilizing yeast, Pichia stipitis NCYC 1541. RESULTS: Pretreatment resulted in a significant lignin removal up to 83.26% and cellulose released up to 80.74% in treated OPT by alkaline peroxide combined with autoclave method. Enzymatic hydrolysis of treated OPT resulted in an increase in fermentable sugar up to 93.22%. Optimization of SSCF by response surface method showed that the coculture could work together to produce maximum ethanol (1.89%) and fermentation efficiency (66.14%) under the optimized condition. CONCLUSION: Pretreatment by alkaline peroxide combined with autoclave method and SSCF process could be expected as a promising system for ethanol production from oil palm trunk and various lignocellulosic biomass.