Effect of Co-Inoculation with Pichia fermentans and Pediococcus acidilactici on Metabolite Produced During Fermentation and Volatile Composition of Coffee Beans

Abstract

Removal of the mucilage layer of coffee fruits by a fermentation process has became an interesting strategy to improve coffee quality, which is able to assist the formation of flavored molecules. In this study, four sets of inoculation protocols were evaluated using ripe and immature coffee fruits, respectively, including (i) pure culture fermentation with Pichia fermentans, (ii) pure culture fermentation with Pediococcus acidilactici, (ii) combined fermentation with P. fermentans and P. acidilactici, and (iv) spontaneous, non-inoculated control. The initial pulp sugar concentration of ripe coffee fruits (0.57 and 1.13 g/L glucose and fructose content, respectively) was significantly higher than immature coffee pulp (0.13 and 0.26 g/L glucose and fructose content, respectively). Combined inoculation with P. fermentans and P. acidilactici of ripe coffee beans increased pulp sugar consumption and production of metabolites (lactic acid, ethanol, and ethyl acetate), evidencing a positive synergic interaction between these two microbial groups. On the other hand, when immature coffee fruits were used, only pure culture inoculation with P. fermentans was able to improve metabolite formation during fermentation, while combined treatment showed no significant effect. Altogether, 30 volatile compounds were identified and semi-quantified with HS- solid phase microextraction (SPME)-gas chromatography coupled to mass spectrophotometry (GC/MS) in fermented coffee beans. In comparison with pure cultures and spontaneous process, combined treatment prominently enhanced the aroma complexity of ripe coffee beans, with a sharp increase in benzeneacetaldehyde, 2-heptanol, and benzylalcohol. Consistent with the monitoring of the fermentation process, only P. fermentans treatment was able to impact the volatile composition of immature coffee beans. The major impacted compounds were 2-hexanol, nonanal, and D-limonene. In summary, this study demonstrated the great potential of the combined use of yeast and lactic acid bacteria to improve fermentation efficiency and to positively influence the chemical composition of coffee beans. Further studies are still required to investigate the mechanisms of synergism between these two microbial groups during the fermentation process and influence the sensory properties of coffee products.

Cocoa bean turning as a method for redirecting the aroma compound profile in artisanal cocoa fermentation

“…Yeasts such as H. opuntiae have been associated with 2-phenylethyl acetate and ethyl hexanoate production ( Hu et al., 2018 ). Esters are mostly produced by the synergy between yeasts and LAB in the anaerobic stage of fermentation ( da Silva Vale et al., 2019 ; Hamdouche et al., 2019 ). The results of this study could indicate a greater production of esters under the B2 method due to the lower aeration incorporated into cocoa-pulp mass as compared to the B1 method.…”

“…Additionally, P. acidilactici was identified under B1 fermentation, which is a species that shows higher production of ethyl acetate when coinoculated with yeasts of the genus Pichia spp. than when grown in isolation ( da Silva-Vale et al., 2019 ).…”

“…On the other hand, B2 fermentation prolonged anaerobic conditions, stimulating the growth of yeasts and LAB, which favored their total dominance during the whole fermentation process. A high production of acetate esters has been associated with better synergy between the coinoculation of yeasts and LAB ( da Silva-Vale et al., 2019 ). Some yeasts isolated from cocoa bean fermentation, such as H. opuntiae and Pichia spp., have been recognized as producers of ethanol, 2-phenylethyl alcohol, esters (such as 2-phenylethyl acetate, ethyl hexanoate, and 2-pentanol acetate), aldehydes (such as 3-methyl butanal and phenylacetaldehyde), and acetophenone ( Cevallos-Cevallos et al., 2018 ; Hu et al., 2018 ; Ouattara et al., 2020 ).…”

Facility‐specific ‘house’ microbiome ensures the maintenance of functional microbial communities into coffee beans fermentation: implications for source tracking

“…These species have been frequently isolated in spontaneous coffee fermentations performed in Australia, Brazil, Colombia, China, Ecuador, and Tanzania (Masoud et al ., 2004; de Melo Pereira et al ., 2014; Evangelista et al ., 2015; Junqueira et al ., 2019; Zhang et al ., 2019a,b; Pothakos et al ., 2020). Pichia and Hanseniaspora are associated with flavour‐active ester production impacting distinct floral and fruity notes in coffee beverages, while Candida species are known to assist in the process of coffee removing mucilage through the production of pectinolytic enzymes (Masoud et al ., 2005; Masoud and Jespersen, 2006; de Melo Pereira et al ., 2014; da Silva et al ., 2019; Giorello et al ., 2019). In addition to yeasts, filamentous fungi belonging to the Order Tremellales and Fusarium were detected within the core microbiome (Fig.…”

Coffee Microbiota and Its Potential Use in Sustainable Crop Management. A Review

“…Using this strategy, they were able to clearly demonstrate the implication of yeasts in the quality improvement of the wetprocessed coffee. Finally, several authors also demonstrated the improvement of the quality after the inoculation of selected yeasts and lactic acid bacteria strains on coffee undergoing not only the wet (De Melo Pereira et al, 2015b, 2016Da Silva Vale et al, 2019;Bressani et al, 2020) but also the semidry processing (Martinez et al, 2017).…”