Grape marcs as unexplored source of new yeasts for future biotechnological applications

Biodiversity and Bioprospecting of Fungal Endophytes from the Antarctic Plant Colobanthus quitensis

Microorganisms from extreme environments are considered as a new and valuable reservoir of bioactive molecules of biotechnological interest and are also utilized as tools for enhancing tolerance to (a)biotic stresses in crops. In this study, the fungal endophytic community associated with the leaves of the Antarctic angiosperm Colobanthus quitensis was investigated as a new source of bioactive molecules. We isolated 132 fungal strains and taxonomically annotated 26 representative isolates, which mainly belonged to the Basidiomycota division. Selected isolates of Trametes sp., Lenzites sp., Sistotrema sp., and Peniophora sp. displayed broad extracellular enzymatic profiles; fungal extracts from some of them showed dose-dependent antitumor activity and inhibited the formation of amyloid fibrils of α-synuclein and its pathological mutant E46K. Selected fungal isolates were also able to promote secondary root development and fresh weight increase in Arabidopsis and tomato and antagonize the growth of pathogenic fungi harmful to crops. This study emphasizes the ecological and biotechnological relevance of fungi from the Antarctic ecosystem and provides clues to the bioprospecting of Antarctic Basidiomycetes fungi for industrial, agricultural, and medical applications.

Study of potential probiotic and biotechnological properties of non-Saccharomyces yeasts from fruit Brazilian ecosystems

Yeast isolates from flowers and fruits from a Brazilian forest were studied. The yeasts were identified at species and strain level by PCR-RFLP and PCR-RAPD, respectively. The 46 isolated yeasts were classified into 11 different species belonging to the genera Candida, Diutina, Hanseniaspora, Meyerozyma, Pichia, Rhodotorula, and Torulaspora. A total of 20 different strains were found. In order to ascertain the probiotic potential, the resistance to gastrointestinal conditions, autoaggregation, and hydrophobicity assays were studied, along with the capacity to form biofilm. The results indicate that, although most of the strains presented better results than Saccharomyces boulardii (the only strain recognized as a probiotic yeast), four strains were the most promising, namely, Rhodotorula mucilaginosa 32, Meyerozyma caribbica 35, and Diutina rugosa 12 and 45, according to the Duncan test. Several biotechnological properties were evaluated. D. rugosa inhibited Dekkera bruxellensis. The assimilation or fermentation of seven sugars was tested, and only five of the yeasts did not show a capacity to assimilate any of the sugars under aerobic conditions. However, all strains were able to ferment at least one of the sugars under anaerobic conditions. As far as enzyme production is concerned, positive results were only found for the enzymes' amylase, pectinase, and protease. D. rugosa 42 and Hanseniaspora opuntiae 18, followed of Pichia kluyveri 26, showed high values for the production of melatonin. In conclusion, the results of this study show that several non-Saccharomyces present probiotic characteristics, and these have good potential for industrial applications in the food or biotechnology industries.

Safety of Lactobacillus plantarum ST8Sh and Its Bacteriocin

Total DNA extracted from Lb. plantarum ST8Sh was screened for the presence of more than 50 genes related to production of biogenic amines (histidine decarboxylase, tyrosine decarboxylase, and ornithine decarboxylase), virulence factors (sex pheromones, gelatinase, cytolysin, hyaluronidase, aggregation substance, enterococcal surface protein, endocarditis antigen, adhesion of collagen, integration factors), and antibiotic resistance (vancomycin, tetracycline, erythromycin, gentamicin, chloramphenicol, bacitracin). Lb. plantarum ST8Sh showed a low presence of virulence genes. Only 13 genes were detected (related to sex pheromones, aggregation substance, adhesion of collagen, tetracycline, gentamicin, chloramphenicol, erythromycin, but not to vancomycin, and bacitracin) and may be considered as indication of safety for application in fermented food products. In addition, interaction between Lb. plantarum ST8Sh and drugs from different groups were determined in order to establish possible application of the strain in combination with commercial drugs. Cytotoxicity of the semi-purified bacteriocins produced by Lb. plantarum ST8Sh was depended on applied concentration-highly cytotoxic when applied at 25 μg/mL and no cytotoxicity at 5 μg/mL.

Genetic variability and physiological traits of Saccharomyces cerevisiae strains isolated from "Vale dos Vinhedos" vineyards reflect agricultural practices and history of this Brazilian wet subtropical area

Vale dos Vinhedos appellation of origin has a very recent history as industrial wine making region. In this study we investigated the genetic and phenotypic variability of Saccharomyces cerevisiae strains isolated from South-Brazilian vineyards in order to evaluate strain fermentation aptitude and copper and sulphites tolerance. Merlot grape bunches were collected from three vineyards and yeast isolation was performed after single bunch fermentation. High genotypic variability was found and most of the genotypes revealed to be vine-specific. No industrial strain dissemination was present in the sampled vineyards, although it has been wildly reported in traditional winemaking countries. From the phenotypic traits analysis these Brazilian native strains showed good fermentation performances, good tolerance to sulphites and, in particular, a high copper tolerance level. Copper is the most important metal in the formulation of fungicides against downy mildew (Plasmopara viticola), one of the most harmful disease of the vines, and other fungal pests. The high tolerance to copper suggests an environmental adaptation to the strong use of copper-based fungicides, requested by the wet subtropical climate.

Biocontrol Ability and Action Mechanism of Starmerella bacillaris (Synonym Candida zemplinina) Isolated from Wine Musts against Gray Mold Disease Agent Botrytis cinerea on Grape and Their Effects on Alcoholic Fermentation

Gray mold is one of the most important diseases of grapevine in temperate climates. This plant pathogen affects plant growth and reduces wine quality. The use of yeasts as biocontrol agents to apply in the vineyard have been investigated in recent years as an alternative to agrochemicals. In this work, fermenting musts obtained from overripe grape berries, therefore more susceptible to infection by fungal pathogens such as Botrytis cinerea, were considered for the selection of yeasts carrying antifungal activity. Thirty-six isolates were identified as Starmerella bacillaris, a species recently proven to be of enological interest. Among them 14 different strains were studied and antifungal activity against B. cinerea was demonstrated, for the first time, to be present in S. bacillaris species. The production of volatile organic compounds (VOCs), tested in vitro, was found to be the main responsible of S. bacillaris antifungal effects. All the strains were able to reduce B. cinerea decay on wounded grape berries artificially inoculated with gray mold. The colonization level of wound was very high reaching, after 5 days, a concentration of 10⁶ cells per ml of grape juice obtained after berry crushing. At this cell concentration S. bacillaris strains were used to ferment synthetic and natural musts. The sequential yeast inoculation, performed by adding S. cerevisiae 48 h after S. bacillaris, was needed to complete sugar consumption and determined a significant increase in glicerol content and a reduction of ethanol and acetic acid concentrations. The high wound colonization ability, found in this work, together with the propensity to colonize grape berry and the interesting enological traits possessed by the selected S. bacillaris strains allow the use of this yeast as biocontrol agent on vine and grape berries with possible positive effects on must fermentation, although the presence of S. cerevisiae is needed to complete the fermentation process. This work introduces new possibilities in wine yeast selection programs in order to identify innovative wine yeasts that are simultaneously antifungal agents in vineyards and alternative wine starters for grape must fermentation and open new perspective to a more integrated strategy for increasing wine quality.

Genome Sequence of Lactobacillus fabifermentans Strain T30PCM01, Isolated from Fermenting Grape Marc

Here, we report the draft genome assembly of Lactobacillus fabifermentans strain T30PCM01 isolated from grape marc. Its genome is the largest (3.58 Mbp) among Lactobacillus species and reveals an enormous potential for carbohydrate utilization and transcriptional regulation.

Exploring grape marc as trove for new thermotolerant and inhibitor-tolerant Saccharomyces cerevisiae strains for second-generation bioethanol production

BACKGROUND

Robust yeasts with high inhibitor, temperature, and osmotic tolerance remain a crucial requirement for the sustainable production of lignocellulosic bioethanol. These stress factors are known to severely hinder culture growth and fermentation performance.

RESULTS

Grape marc was selected as an extreme environment to search for innately robust yeasts because of its limited nutrients, exposure to solar radiation, temperature fluctuations, weak acid and ethanol content. Forty newly isolated Saccharomyces cerevisiae strains gave high ethanol yields at 40°C when inoculated in minimal media at high sugar concentrations of up to 200 g/l glucose. In addition, the isolates displayed distinct inhibitor tolerance in defined broth supplemented with increasing levels of single inhibitors or with a cocktail containing several inhibitory compounds. Both the fermentation ability and inhibitor resistance of these strains were greater than those of established industrial and commercial S. cerevisiae yeasts used as control strains in this study. Liquor from steam-pretreated sugarcane bagasse was used as a key selective condition during the isolation of robust yeasts for industrial ethanol production, thus simulating the industrial environment. The isolate Fm17 produced the highest ethanol concentration (43.4 g/l) from the hydrolysate, despite relatively high concentrations of weak acids, furans, and phenolics. This strain also exhibited a significantly greater conversion rate of inhibitory furaldehydes compared with the reference strain S. cerevisiae 27P. To our knowledge, this is the first report describing a strain of S. cerevisiae able to produce an ethanol yield equal to 89% of theoretical maximum yield in the presence of high concentrations of inhibitors from sugarcane bagasse.

CONCLUSIONS

This study showed that yeasts with high tolerance to multiple stress factors can be obtained from unconventional ecological niches. Grape marc appeared to be an unexplored and promising substrate for the isolation of S. cerevisiae strains showing enhanced inhibitor, temperature, and osmotic tolerance compared with established industrial strains. This integrated approach of selecting multiple resistant yeasts from a single source demonstrates the potential of obtaining yeasts that are able to withstand a number of fermentation-related stresses. The yeast strains isolated and selected in this study represent strong candidates for bioethanol production from lignocellulosic hydrolysates.