The aim of this study was to develop a kefir apple-based vinegar and evaluate this fermentation process using new methodology with Biospeckle Laser. Brazilian kefir grains were inoculated in apple must for vinegar production. In this study, the microbial community present in kefir, and correspondent vinegar, was investigated using Matrix Assisted Laser Desorption/Ionization – Time of Flight Mass Spectrometry (MALDI-TOF MS) technique. Saccharomyces cerevisiae, Lactobacillus paracasei, Lactobacillus plantarum, Acetobacter pasteurianus and Acetobacter syzygii were the microbial species identified. S. cerevisiae, L. plantarum, A. pasteurianus and A. syzygii were found in smaller quantities at the beginning of the alcoholic fermentation, but were found throughout the alcoholic and acetic fermentation. Kefir grains were able to utilize apple must as substrate to produce ethanol, and acetic acid. Acetate, volatile alcohols and aldehydes in the vinegar-based kefir were also produced. The yield of acetic acid in the kefir vinegars was ∼79%. The acetic acid concentration was ∼41 g L−1, reaching the required standard for the Brazilian legislation accepts it as vinegar (4.0% acetic acid). Kefir vinegar showed good acceptance in the sensory analysis. The technology proposed here is novel by the application of immobilized-cell biomass (kefir grains) providing a mixed inocula and eliminating the use of centrifuge at the end of the fermentative process. This step will save energy demand and investment. This is the first study to produce apple vinegar using kefir grains.

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Malassezia species are part of human commensal microbiota and is also related to diseases. Little is known about the interaction of these microorganisms with their host. Here we established two standard culture conditions for Malassezia spp. to perform infection assays using C. elegans and T. molitor. Invertebrate hosts infected by Malassezia spp. cultured in M9M resulted in higher death rate on survival assays when compared to yeasts cultured in standard Dixon medium indicating that M9M cultured Malassezia species have increased virulence. The culture and infection conditions established in this work, using invertebrate alternative models, are valuable tools to understand Malassezia-host interaction.

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RESUMOThe aim of this study was to evaluate the use of Maldi-Tof MS biosensor in microbial assessment of Brazilian kefir grains. Maldi-Tof MS is a new methodology for the rapid diagnosis of microorganisms. A total of 358 microorganisms were isolated, 31 were yeasts and 327 were bacteria (divided into lactic and acetic bacteria). Microbial colonies were grown in Luria-Bertani agar medium and incubated at 35 °C for 18h and used in the identification of species by Maldi-Tof MS. The microbial population identified in Brazilian kefir grains was Lactobacillus paracasei, Saccharomyces cerevisiae, Lactobacillus plantarum, Acetobacter pasteurianus, and Acetobacter syzygii. This study demonstrated a rapid and accurate identification of the Brazilian kefir grains microorganisms using the Maldi-Tof MS biosensor. In conclusion, the Maldi-Tof MS technology can facilitate the microbiological control in a fermentation process using kefir grains as starter cultures.O objetivo deste estudo foi avaliar o uso do biossensor de Maldi-Tof MS na avaliação microbiana de grãos de kefir. Maldi-Tof MS é uma nova metodologia para o diagnóstico rápido de micro-organismos. Um total de 358 microorganismos foram isolados, 31 foram leveduras e 327 foram bactérias (divididas em bactérias láticas e acéticas). Colônias microbianas foram cultivadas em meio Luria-Bertani (LB) e incubadas a 35 °C por 18h e posteriormente utilizadas na identificação a nível de espécies pelo Maldi-Tof MS. A população microbiana identificada nos grãos de kefir brasileiros foi Lactobacillus paracasei, Saccharomyces cerevisiae, Lactobacillus plantarum, Acetobacter pasteurianus e Acetobacter syzygii. Este estudo demonstrou uma identificação rápida e precisa dos micro-organismos de grãos de kefir brasileiros utilizando o biossensor Maldi-Tof MS. Em conclusão, a tecnologia Maldi-Tof MS pode facilitar o controle microbiológico em um processo de fermentação usando grãos de kefir como culturas iniciadoras. Palavras-chave: micro-organismos; bactérias; levedura; sensor biológico.This is an open access article under the CC BY licence Creative Commons 73 Use of Maldi-Tof MS biosensor in microbial assessment of Brazilian kefir grains 1