Diversidade e potencial tecnológico de leveduras isoladas de queijo de coalho produzido em Pernambuco

Derivado do leite cru ou pasteurizado, o queijo de coalho artesanal é um alimento popularmente consumido na região Nordeste do Brasil. Ele apresenta uma diversidade microbiana de grande importância para a indústria de laticínios, assim como também os aspectos econômicos e de segurança alimentar. Entre a microbiota presente no queijo de coalho, estão as leveduras que atualmente vêm sendo destaque por apresentarem grande potencial para aplicação no mercado alimentício. Nesse sentido, o presente estudo teve por objetivo isolar, identificar e caracterizar leveduras presentes nos queijos de coalho produzidos em três municípios de Pernambuco (Arcoverde, Capoeiras e Venturosa). Para a identificação das leveduras foram utilizados testes bioquímicos e fenotípicos, seguida da caracterização destas leveduras quanto a: patogenicidade, produção de diacetil e da enzima digestiva, β-galactosidase. Os resultados revelaram a presença de quinze leveduras, sendo duas do queijo de Venturosa e treze do queijo de Arcoverde. Dentre esses isolados, foi possível identificar os gêneros Dekkera, Pichia, Debaryomyces, Rhodotorula, Saccharomyces, Galactomyces e Candida, sendo este último o mais predominante. Algumas espécies produziram diacetil, com maior concentração produzida pela Pichia minuta. Por outro lado, todas as espécies produziram β-galactosidase, intracelular e extracelular, se destacando como melhor produtora a espécie Candida versatilis (33,85 U/mL). Além disso, segundo testes de patogenicidade, nenhuma das leveduras oferece risco à saúde humana. Com esses resultados preliminares é possível inferir que algumas cepas isoladas do queijo de coalho artesanal têm potencial tecnológico, porém, testes complementares são cruciais para propô-las ao mercado produtor de laticínios.

Isolation and identification of halophilic microorganisms in soy sauce

Microorganisms play an important role in the fermentation of soy sauce as they produce flavoring compounds which contribute to the desired taste and quality of soy sauce. The aim of this study was to isolate and identify halophilic microorganisms that are involved in the first stage (Koji) and second stage (Moromi) of soy sauce fermentation. In this study, soy sauce samples were collected from a local company located in Johor Bahru. The microorganisms were identified using Analytical Profile Identification (API) system and 16s ribosomal RNA (bacteria)/Internal Transcribed Spacer region (fungi and yeast) sequencing. In the koji fermentation, one fungus was isolated and identified as Aspergillus oryzae. During the moromi fermentation, one lactic acid bacteria and two yeasts were identified, including Tetragenococcus halophilus, Candida versatilis and Candida etchellsii. These halophilic microorganisms can be used as starter culture in moromi stage to shorten the fermentation period.

Can Interspecies Hybrid Zygosaccharomyces rouxii Produce an Allohaploid Gamete?

ABSTRACT In soy sauce manufacturing, Candida versatilis plays a role in the production of volatile flavor compounds, such as volatile phenols, but limited accessible information on its genome has prevented further investigation regarding aroma production and breeding. Although the draft genome sequence data of two strains of C. versatilis have recently been reported, these strains are not similar to each other. Here, we reassess the draft genome sequence data for strain t-1, which was originally reported to be C. versatilis, and conclude that strain t-1 is most probably not C. versatilis but a gamete of hybrid Zygosaccharomyces rouxii. Phylogenetic analysis of the D1/D2 region of the 26S ribosomal DNA (rDNA) sequence indicated that strain t-1 is more similar to the genus Zygosaccharomyces than to C. versatilis. Moreover, we found that the genome of strain t-1 is composed of haploid genome content and divided into two regions that show approximately 100% identity with the T or P subgenome derived from the natural hybrid Zygosaccharomyces rouxii, such as NBRC110957 and NBRC1876. We also found a chromosome crossing-over signature in the scaffolds of strain t-1. These results suggest that strain t-1 is a gamete of the hybrid Z. rouxii, generated by either meiosis or chromosome loss following reciprocal translocation between the T and P subgenomes. Although it is unclear why strain t-1 was misidentified as C. versatilis, the genome of strain t-1 has broad implications for considering the evolutionary fate of an allodiploid. IMPORTANCE In yeast, crossing between different species sometimes leads to interspecies hybrids. The hybrid generally cannot produce viable spores because dissimilarity of parental genomes prevents normal chromosome segregation during meiotic division, leading to a dead end. Thus, only a few natural cases of homoploid hybrid speciation, which requires mating between 1n gametes of hybrids, have been described. However, a recent study provided strong evidence that homoploid hybrid speciation is initiated in natural populations of the budding yeast, suggesting the potential presence of viable 1n gametes of hybrids. The significance of our study is finding that the strain t-1, which had been misidentified as Candida versatilis, is a viable 1n gamete derived from hybrid Zygosaccharomyces rouxii.

Carbon metabolism and transcriptional variation in response to salt stress in the genome shuffled Candida versatilis and a wild-type salt tolerant yeast strain

The carbon metabolism and molecular mechanisms of adaptation response when exposed to conditions causing osmotic stress in strains of a wild-type of Candida versatilis (WT) and S3–5 were investigated.