In silico genomic insights into aspects of food safety and defense mechanisms of a potentially probiotic Lactobacillus pentosus MP-10 isolated from brines of naturally fermented Aloreña green table olives.

Lactobacillus pentosus MP-10, isolated from brines of naturally fermented Aloreña green table olives, exhibited high probiotic potential. The genome sequence of L. pentosus MP-10 is currently considered the largest genome among lactobacilli, highlighting the microorganism's ecological flexibility and adaptability. Here, we analyzed the complete genome sequence for the presence of acquired antibiotic resistance and virulence determinants to understand their defense mechanisms and explore its putative safety in food. The annotated genome sequence revealed evidence of diverse mobile genetic elements, such as prophages, transposases and transposons involved in their adaptation to brine-associated niches. In-silico analysis of L. pentosus MP-10 genome sequence identified a CRISPR (clustered regularly interspaced short palindromic repeats)/cas (CRISPR-associated protein genes) as an immune system against foreign genetic elements, which consisted of six arrays (4-12 repeats) and eleven predicted cas genes [CRISPR1 and CRISPR2 consisted of 3 (Type II-C) and 8 (Type I) genes] with high similarity to L. pentosus KCA1. Bioinformatic analyses revealed L. pentosus MP-10 to be absent of acquired antibiotic resistance genes, and most resistance genes were related to efflux mechanisms; no virulence determinants were found in the genome. This suggests that L. pentosus MP-10 could be considered safe and with high-adaptation potential, which could facilitate its application as a starter culture and probiotic in food preparations

Exopolysaccharide (EPS) synthesis by oenococcus oeni: from genes to phenotypes

Oenococcus oeni is the bacterial species which drives malolactic fermentation in wine. The analysis of 50 genomic sequences of O. oeni (14 already available and 36 newly sequenced ones) provided an inventory of the genes potentially involved in exopolysaccharide (EPS) biosynthesis. The loci identified are: two gene clusters named eps1 and eps2, three isolated glycoside-hydrolase genes named dsrO, dsrV and levO, and three isolated glycosyltransferase genes named gtf, it3, it4. The isolated genes were present or absent depending on the strain and the eps gene clusters composition diverged from one strain to another. The soluble and capsular EPS production capacity of several strains was examined after growth in different culture media and the EPS structure was determined. Genotype to phenotype correlations showed that several EPS biosynthetic pathways were active and complementary in O. oeni. Can be distinguished: (i) a Wzy -dependent synthetic pathway, allowing the production of heteropolysaccharides made of glucose, galactose and rhamnose, mainly in a capsular form, (ii) a glucan synthase pathway (Gtf), involved in β-glucan synthesis in a free and a cell-associated form, giving a ropy phenotype to growth media and (iii) homopolysaccharide synthesis from sucrose (α-glucan or β-fructan) by glycoside-hydrolases of the GH70 and GH68 families. The eps gene distribution on the phylogenetic tree was examined. Fifty out of 50 studied genomes possessed several genes dedicated to EPS metabolism. This suggests that these polymers are important for the adaptation of O. oeni to its specific ecological niche, wine and possibly contribute to the technological performance of malolactic starters

Implications of new research and technologies for malolactic fermentation in wine

The initial conversion of grape must to wine is an alcoholic fermentation (AF) largely carried out by one or more strains of yeast, typically Saccharomyces cerevisiae. After the AF, a secondary or malolactic fermentation (MLF) which is carried out by lactic acid bacteria (LAB) is often undertaken. The MLF involves the bioconversion of malic acid to lactic acid and carbon dioxide. The ability to metabolise L-malic acid is strain specific, and both individual Oenococcus oeni strains and other LAB strains vary in their ability to efficiently carry out MLF. Aside from impacts on acidity, LAB can also metabolise other precursors present in wine during fermentation and, therefore, alter the chemical composition of the wine resulting in an increased complexity of wine aroma and flavour. Recent research has focused on three main areas: enzymatic changes during MLF, safety of the final product and mechanisms of stress resistance. This review summarises the latest research and technological advances in the rapidly evolving study of MLF and investigates the directions that future research may take.Krista M. Sumby, Paul R. Grbin, Vladimir Jirane