Yeast dynamics in the black table olives processing using fermented brine as starter

Spontaneous fermentation with autochthonous yeasts is the most traditional method used for the production of black table olives, which requires minimal intervention. The aim of this study was to evaluate the effects of adding a brine starter, developed from one-year spontaneously fermented black table olives, on the microbiological, chemical, and sensory characteristics of naturally fermented Taggiasca table olives. The olives were fermented in brine containing 12% (w/v) NaCl with 0.6% (w/v) citric acid and inoculated with a selected brine starter containing primarily Pichia manshurica (87% predominance) and Saccharomyces cerevisiae (10% predominance). Brine and olives samples were analysed at the start of the experiment and after 3, 6, 9, and 12 months of fermentation. The P. manshurica and S. cerevisiae present in the brine starter drove the entire fermentation process, along with other autochthonous species that were not included in the starter, including Zygosaccharomyces mrakii. Spoilage microorganisms and undesired off-odours and off-flavours were not present at the end of fermentation. When compared to the control, the use of the brine starter increased the total yeast population in the brine during the first 6 months of fermentation, thus shortening the debittering time of the fruits and improving the taste complexity of the final product.

156 Effect of Anti-yeast on Sugarcane Silage Gas Production

Although sugarcane produces a large amount of energy per hectare, its ensiled storage leads to losses, which makes it one of the most expensive options for animal feeding. These losses occur due to fermentation of sugars and organic acids by yeasts, producing alcohol and gas. Inoculants containing Lactobacillus buchneri increase acetic acid production, which has effect against yeast. In this study, we produced egg yolk antibodies (IgY) against yeasts that ferment lactate (Candida glabrata, Pichia kudriavzevii, and Pichia manshurica) and sugar (Saccharomyces cerevisiae, Torulospora delbrueckii, Schizosaccharomyces pombe and Debaryomyces etchellsii) isolated in sugarcane silage. Shortly before ensiling, doses of 0, 175, 350, and 700 g/t IgY, and Lactobacillus buchneri were applied to chopped forage. Gas losses were calculated using experimental silos in triplicate, according to the equation: G = (PCf - PCa)/(MFf) × 100, in which: G = gas losses (kg/t); PCf = weight of full silo (equipped with a Bunsen valve to allow gas outflow) at sealing (kg); PCa = weight of full bucket at opening (kg); MFf = forage mass at sealing (kg). The data were analyzed as a completely randomized design and submitted to analysis of variance and regression using the SAS (SAS, 1998), which was chosen because of the significance of the regression parameters, tested by Tukey’s test (P < 0.05) and the values of the coefficients of determination. Thirty days after sealing the L. buchneri inoculant and doses of 350 and 700 g/t IgY promoted less gas losses than control that had no any product (12.74; 15.59 and 15.28 versus 27.74, respectively, P < 0.05) and the L. buchneri did not differ from IgY doses. The gas losses decreased quadratically with the anti-yeast addition, estimating maximum of 530 g/t fresh forage. We conclude that anti-yeast use reduces gas production during fermentation. With continuity of this research, we may obtain a roughage with higher nutritional value, as its mode of action in yeast control does not involve consumption of sugars or organic acids.

Adhesion Properties, Biofilm Forming Potential, and Susceptibility to Disinfectants of Contaminant Wine Yeasts

In this study, yeasts isolated from filter membranes used for the quality control of bottled wines were identified and tested for their resistance to some cleaning agents and potassium metabisulphite, adhesion to polystyrene and stainless-steel surfaces, and formation of a thin round biofilm, referred to as a MAT. A total of 40 strains were identified by rRNA internal transcribed spacer (ITS) restriction analysis and sequence analysis of D1/D2 domain of 26S rRNA gene. Strains belong to Pichia manshurica (12), Pichia kudriavzevii (9), Pichia membranifaciens (1), Candida sojae (6), Candida parapsilosis (3), Candida sonorensis (1), Lodderomyces elongisporus (2), Sporopachydermia lactativora (3), and Clavispora lusitaniae (3) species. Regarding the adhesion properties, differences were observed among species. Yeasts preferred planktonic state when tested on polystyrene plates. On stainless-steel supports, adhered cells reached values of about 6 log CFU/mL. MAT structures were formed only by yeasts belonging to the Pichia genus. Yeast species showed different resistance to sanitizers, with peracetic acid being the most effective and active at low concentrations, with minimum inhibitory concentration (MIC) values ranging from 0.08% (v/v) to 1% (v/v). C. parapsilosis was the most sensible species. Data could be exploited to develop sustainable strategies to reduce wine contamination and establish tailored sanitizing procedures.

Use of Air-Protected Headspace to Prevent Yeast Film Formation on the Brine of Leccino and Taggiasca Black Table Olives Processed in Industrial-Scale Plastic Barrels

The formation of yeast film on the brine of black table olives during fermentation in plastic barrels on an industrial-scale could be critical for the quality of the product. In order to prevent the formation of yeast film on the brine surface, a structural modified industrial barrel, which excludes oxygen from the headspace, was tested. Tests carried out during two years indicated that the yeast film contamination reached the maximum values at eight months of fermentation, equal to 19% and 24% respectively, for the Taggiasca and Leccino olives, processed in unmodified industrial plastic barrels. No yeast films formed on brines from the same varieties of olives processed in the modified plastic barrels. The brines of both varieties of olives processed in the industrial barrels displayed three dominant yeast species, while five species were detected in the brines from the modified barrels. Wickerhamomyces anomalus and Pichia manshurica were the main producers of yeast films. However, P. manshurica unlike the other yeasts, has shown also a biotype unable to produce films on the brine of the olives. The brines of Leccino and Taggiasca processed in the modified barrels, compared to the control, showed a higher titratable acidity and a higher concentration of CO2 useful to prevent the yeast film formation.

Fate of Spoilage and Pathogenic Microorganisms in Acidified Cold-Filled Hot Pepper Sauces

ABSTRACT Consumption of spicy foods and hot sauces is currently a popular trend worldwide. Shelf-stable acidified sauces are commonly hot-filled to ensure commercial sterility, but cold-fill-hold processes might also be suitable if microbial safety and stability are ensured. For this study, model acidified hot pepper sauces were developed and characterized. The effects of sauce pH and of two different organic acids on the survival of Pichia manshurica and Lactobacillus curvatus isolated from contaminated commercial hot sauces and on pathogenic Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes were assessed. Full factorial designs with three levels for pH (3.2, 3.5, and 3.9) and two for organic acid (citric and acetic) were used to determine the effects of these factors and their interactions on the survival of the microorganisms. Commercially sterile sauces were independently inoculated and kept at ambient temperature. Microbial counts were determined at different sampling times, depending on the treatment evaluated. Sauces acidified to pH 3.2 with citric or acetic acid were inoculated with cocktails of five strains or serotypes of the three pertinent pathogens, and inactivation curves were determined. Trials were performed in triplicate. A greater than 5-log reduction of P. manshurica and L. curvatus was achieved in less than 6 h in sauces adjusted to pH 3.2 with acetic acid. Greater than 5-log reductions of pathogenic bacteria were achieved 0.5 h after inoculation in sauces acidified to pH 3.2 with acetic acid. In contrast, at least 48 h was required to guarantee the same inactivation for the most tolerant pathogen when citric acid was used. Thus, a cold-fill-hold process may be a suitable alternative for acidified hot pepper sauces. Based on survival of the microorganisms evaluated in this study, microbial safety and stability can be achieved by adjusting the pH to 3.2 or less by the addition of acetic acid.

Draft Genome Sequence of the Yeast Pichia manshurica YM63, a Participant in Secondary Fermentation of Ishizuchi-Kurocha, a Japanese Fermented Tea

ABSTRACT Pichia manshurica is common in fermentation; however, genome analysis has never been reported for the species. This yeast plays a role in the secondary fermentation of Ishizuchi-kurocha, a traditional Japanese fermented tea. This paper presents the draft genome sequence of P. manshurica YM63, isolated from the leaves of fermented tea.

Diversity of yeasts during fermentation of cocoa from two sites in the Brazilian Amazon

ABSTRACT The purpose of this study was to identify the yeasts involved in spontaneous fermentation of cocoa from the Brazilian Amazon region. The fermentation process was carried out experimentally with cocoa seeds from two sites (Medicilândia and Tucumã), State of Pará, northern Brazil, during a six-day period. Totals of 44 yeasts were isolated from Medicilândia and 29 from Tucumã. Molecular identification was carried out by sequencing the D1/D2 region fragment of the rRNA 26S gene, expanded with universal primers for the NL1GC and LS2 eukaryotes. Pichia manshurica and Saccharomyces cerevisiae were identified in Medicilândia and five yeast species (Pichia fermentans, P. kudriavzevii, P. manshurica, S. cerevisiae and Zygosaccharomyces bailii) were identified in Tucumã. The results showed that P. manshurica and S. cerevisiae may have potential for use as starter cultures in future studies to improve the quality of cocoa seeds fermented in the Brazilian Amazon region.

Isolation, identification and diversity of oleaginous yeasts from Kuching, Sarawak, Malaysia

Vincent M, Hung MC, Baran PRM, Azahari AS, Adeni DSA. 2018. Isolation, identification and diversity of oleaginous yeastsfrom Kuching, Sarawak, Malaysia. Biodiversitas 19: 1266-1272. The present study was performed to isolate, identify and determine thediversity of oleaginous yeasts from various sources in Kuching, Sarawak (Malaysia). Microscopic observations via light and scanningelectron microscope (SEM) indicated that the yeast isolates were in sizes ranging from 2-3 μm in width and 4-8 μm in length, typical ofmost unicellular ascomycotic fungi. Polymerase Chain Reaction (PCR) and molecular identification performed on the yeast isolates,targeting the D1/D2 region of the 26S rDNA, identified 6 yeast species from the 21 isolates, namely Pichia manshurica (5/21), Candidakrusei (8/21), Candida parapsilosis (1/21), Pichia guilliermondii (2/21), Clavispora lusitaniae (1/21) and Kluyveromyces marxianus(4/21). All 21 yeast isolates accumulated intracellular lipids when grown in nitrogen-limited medium, as tested via Sudan IV staining.The present study is the first to document the production of lipids bodies in C. krusei, C. parapsilosis, and C. lusitaniae. Furtherinvestigations to assess the growth kinetics, lipid production efficiencies and lipids profiles of these oleaginous yeasts may provideinsights into the possible utilization of these isolates for a variety of scientific, technical and industrial applications.