title: Isolation, selection and evaluation of yeasts for use in fermentation of coffee beans by the wet process.
abstract: During wet processing of coffee, the ripe cherries are pulped, then fermented and dried. This study reports an experimental approach for target identification and selection of indigenous coffee yeasts and their potential use as starter cultures during the fermentation step of wet processing. A total of 144 yeast isolates originating from spontaneously fermenting coffee beans were identified by molecular approaches and screened for their capacity to grow under coffee-associated stress conditions. According to ITS-rRNA gene sequencing, Pichia fermentans and Pichia kluyveri were the most frequent isolates, followed by Candida Candida glabrata, quercitrusa, Saccharomyces sp., Pichia guilliermondii, Pichia caribbica and Hanseniaspora opuntiae. Nine stress-tolerant yeast strains were evaluated for their ability to produce aromatic compounds in a coffee pulp simulation medium and for their pectinolytic activity. P. fermentans YC5.2 produced the highest concentrations of flavor-active ester compounds (viz., ethyl acetate and isoamyl acetate), while Saccharomyces sp. YC9.15 was the best pectinase-producing strain. The potential impact of these selected yeast strains to promote flavor development in coffee beverages was investigated for inoculating coffee beans during wet fermentation trials at laboratory scale. Inoculation of a single culture of P. fermentans YC5.2 and co-culture of P. fermentans YC5.2 and Saccharomyces sp. YC9.15 enhanced significantly the formation of volatile aroma compounds during the fermentation process compared to un-inoculated control. The sensory analysis indicated that the flavor of coffee beverages was influenced by the starter cultures, being rated as having the higher sensory scores for fruity, buttery and fermented aroma. This demonstrates a complementary role of yeasts associated with coffee quality through the synthesis of yeast-specific volatile constituents. The yeast strains P. fermentans YC5.2 and Saccharomyces sp. YC9.15 have a great potential for use as starter cultures in wet processing of coffee and may possibly help to control and standardize the fermentation process and produce coffee beverages with novel and desirable flavor profiles.
authors.affiliation: Bioprocess Engineering and Biotechnology Department, Federal University of Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: Gilberto Vinícius
authors.initials: GV
authors.lastname: de Melo Pereira
authors.affiliation: Bioprocess Engineering and Biotechnology Department, Federal University of Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: Vanete Thomaz
authors.initials: VT
authors.lastname: Soccol
authors.affiliation: Biotechnology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum695 019, India.
authors.forename: Ashok
authors.initials: A
authors.lastname: Pandey
authors.affiliation: Bioprocess Engineering and Biotechnology Department, Federal University of Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: Adriane Bianchi Pedroni
authors.initials: AB
authors.lastname: Medeiros
authors.affiliation: Department of Agriculture, Coffee Science Division, Federal University of Lavras (UFLA), Lavras, MG, Brazil.
authors.forename: João Marcos Rodrigues
authors.initials: JM
authors.lastname: Andrade Lara
authors.affiliation: Bioprocess Engineering and Biotechnology Department, Federal University of Paraná (UFPR), Curitiba, PR, Brazil.
authors.forename: André Luiz
authors.initials: AL
authors.lastname: Gollo
authors.affiliation: Bioprocess Engineering and Biotechnology Department, Federal University of Paraná (UFPR), Curitiba, PR, Brazil. Electronic address: soccol@ufpr.br.
authors.forename: Carlos Ricardo
authors.initials: CR
authors.lastname: Soccol
mesh_terms: D001628:Beverages / Q000592:standards; D003069:Coffee / Q000378:metabolism* / Q000382:microbiology*; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005285:Fermentation; D005638:Fruit / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D050296:Microbial Viability; D008969:Molecular Sequence Data; D009812:Odorants / Q000032:analysis; D011096:Polygalacturonase / Q000378:metabolism; D012335:RNA, Ribosomal; D013312:Stress, Physiological; D013649:Taste; D015003:Yeasts / Q000201:enzymology / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D003069:Coffee; D021903:DNA, Ribosomal Spacer; D012335:RNA, Ribosomal; D011096:Polygalacturonase
keywords: Aromatized coffee; Pectinolytic enzymes; Pichia fermentans; Saccharomyces sp.; Wet processing