Title: Screening of lactic acid bacteria and yeast strains to select adapted anti-fungal co-cultures for cocoa bean fermentation
Authors : Romanens, Edwina
Freimüller Leischtfeld, Susette
Volland, Andrea
Stevens, Marc
Krähenmann, Ursina
Isele, Désirée
Fischer, Birgit
Meile, Leo
Miescher Schwenninger, Susanne
Published in : International Journal of Food Microbiology
Volume(Issue) : 290
Pages : 262
Pages to: 272
Publisher / Ed. Institution : Elsevier
Issue Date: 2018
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subjects : Lactic acid bacteria; Yeast; Cocoa bean fermentation; Anti-fungal culture; Functional culture; Screening; Food Microbiology; Mycotoxin; Filamentous fungi; Stress tolerance; Agar plate assay; Metabolism
Subject (DDC) : 664: Food technology
Abstract: Contamination with filamentous fungi during cocoa bean fermentation and drying reduces the quality of cocoa beans and poses a health risk for consumers due to the potential accumulation of mycotoxins. The aim of this study was to develop anti-fungal lactic acid bacteria (LAB)-yeast co-cultures by selecting anti-fungal strains best adapted to the cocoa bean fermentation process from 362 LAB and 384 yeast strains isolated from cocoa bean post-harvest processes. The applied multiphasic screening approach included anti-fungal activity tests in vitro and in vivo and assessment of the carbon metabolism and stress tolerance of the anti-fungal strains in cocoa pulp simulation medium. The anti-fungal strains, Lactobacillus fermentum M017, Lactobacillus fermentum 223, Hanseniaspora opuntiae H17, and Saccharomyces cerevisiae H290, were selected based on their high inhibition capacity and their well-adapted metabolism. Up to seven filamentous fungal strains of the genera Aspergillus, Penicillium, and Gibberella were inhibited by 63 and 75% of the maximal inhibition zone by M017 and 223, respectively, and by 25 and 31% by the strains H17 and H290, respectively. Both Lb. fermentum strains converted the medium's glucose, fructose, and citric acid into 20.4–23.0 g/l of mannitol, 3.9–6.2 g/l acetic acid, and 8.6–10.3 g/l lactic acid, whereas the two yeast strains metabolized glucose and fructose to produce 7.4–18.4 g/l of ethanol. The Lb. fermentum strains were further characterized as ethanol, acetic acid, and temperature tolerant and both yeast strains as ethanol and lactic acid tolerant. Finally, the anti-fungal in vivo assays revealed that the two Lb. fermentum strains completely inhibited growth of the citrinin-producing strain, P. citrinum S005, and the potentially fumonisin-producing strain, G. moniliformis S003, on the surface of cocoa beans. All four selected anti-fungal strains, i.e. Lb. fermentum M017, Lb. fermentum 223, H. opuntiae H17, and Sacc. cerevisiae H290, inhibited at 51–95% growth of aflatoxin-producer A. flavus S075 as single cultures while preventing its growth by 100% when combined into four co-cultures, each composed of a Lb. fermentum strain and one of the two yeast strains. As a conclusion, these four LAB-yeast co-cultures are recommended for future applications to limit the growth of filamentous fungi and the concomitant mycotoxin production during the fermentation of cocoa beans.
Departement: Life Sciences and Facility Management
Organisational Unit: Institute of Food and Beverage Innovation (ILGI)
Publication type: Article in scientific Journal
DOI : 10.1016/j.ijfoodmicro.2018.10.001
ISSN: 0168-1605
URI: https://digitalcollection.zhaw.ch/handle/11475/11681
Appears in Collections:Publikationen Life Sciences und Facility Management

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