GC/MS-based metabolic profiling for the evaluation of solid state fermentation to improve quality of Arabica coffee beans.

INTRODUCTION: Coffee fermentation has been reported as one key process in aroma and flavor development of coffee. However, natural fermentation often results in inconsistent quality of coffee. In this study, second fermentation using isolates from feces of civet (Luwak) and Cilembu sweet potato were used to improve the quality of Arabica green coffee beans. OBJECTIVES: The aim of this research was to improve the quality of various Arabica coffee from different origins in Indonesia by controlled-second fermentation. METHOD: The Arabica coffee beans used in this study were from three origins in Indonesia: Kintamani-Bali (I), Aceh-Gayo (II) and Nagarawangi-Sumedang (III). The second fermentation was done using three bacterial isolates coded as BF5C(2); UciSp14; and AF7E which belong to Bacillus genus. Quality assessment of fermented coffee was performed by cupping test following Specialty Coffee Association of America (SCAA) protocol by licensed Q graders, GC/MS metabolite profiling, and total polyphenol content measurement. RESULTS: The controlled-second fermentation for 4-8 h was successful to increase total polyphenol content well as to improve the complexity of coffee taste and coffee quality (cupping score > 84). Comparative GC/MS analysis showed that fermentation of coffee beans resulted in alteration of metabolite profiles of coffee beans compared with control, while still maintaining the characteristics of coffee based on each origin. CONCLUSION: The controlled-second fermentation was effective to increase the quality of coffee and alter metabolite composition of coffee that were associated with changes in taste profile of coffee. This report may serve as basis for producing coffee with better taste quality with higher polyphenols content through standardized fermentation production in industrial scale.

Co-digestion approach for enhancement of biogas production by mixture of untreated napier grass and industrial hydrolyzed food waste.

The co-digestion of untreated Napier grass (NG) and industrial hydrolyzed food waste (FW) was carried out in the batch reactor to investigate the effect of substrate ratios on biogas production performance. Two-stage anaerobic digestion was performed with an initial substrate concentration of 5 g VSadded/L and a Food to Microorganism Ratio (F/M) of 0.84. The 1:1 ratio of the NG and FW showed the optimum performances on biogas production yield with a value of 1,161.33 mL/g VSadded after 60 days of digestion. This was followed by the data on methane yield and concentration were 614.37 mL/g VSadded and 67.29%, respectively. The results were similar to the simulation results using a modified Gompertz model, which had a higher potential methane production and maximum production rate, as well as a shorter lag phase and a coefficient of determination of 0.9945. These findings indicated that the co-digestion of Napier grass and hydrolyzed food waste can enhance biogas production in two-stage anaerobic digestion.

Comparison of thermal alkaline pretreatment and zinc acetate-catalyzed methanolysis (MtOH-ZnOAc) for anaerobic digestion of bioplastic waste.

The aim of this work was to study the effect of thermal alkaline pretreatment and zinc acetate-catalyzed methanolysis (MtOH-ZnOAc) in biogas production from bioplastic in anaerobic digestion. The pretreated bioplastic with MtOH-ZnOAc performs efficient solubilization and produced 205.7 ± 6.9 mL/g CODadded, which is higher than thermal alkaline degradation. The mesophilic condition produces more than 79% higher biogas compared with the thermophilic condition with the diluted pretreated bioplastic by 30 times. The kinetic study was well fit the experimental data and showed the correlation between cumulative biogas, production rate, and lag phase with mono- and two-stage system in batch fermentation. The two-stage system produced 315.6 ± 7.7 mL/g CODadded which was higher 67.2 ± 2.02 than the mono-stage system. Methanosaetaceae predominates among the Archaea, which are primarily responsible for methanogenesis, showing a contribution to a higher biogas production rate.