Survival patterns of Dekkera bruxellensis in wines and inhibitory effect of sulphur dioxide

The wine spoilage yeast species Dekkera bruxellensis, after inoculation in red wines, displayed three survival patterns characterized by: i) initial lag phase followed by growth and sequential death; ii) initial death phase leading to reduced viable counts followed by growth and sequential death; and iii) death phase leading to complete loss of viability. These survival patterns were observed for the same strain in different dry red wine blends with 12% (v/v) ethanol and pH 3.50, in the absence of free sulphur dioxide. For the same wine blend, these patterns also varied with the tested strain. Under laboratory conditions the addition of 150 mg/l of potassium metabisulphite (PMB) to dry red wine with 12% (v/v) ethanol and pH 3.50 reduced initial cell counts by more than 6 logarithmic cycles, inducing full death within less than 24 h. Winery trials showed that D. bruxellensis blooms were only prevented in the presence of about 40 mg/l of free sulphur dioxide in dry red wine, with 13.8% (v/v) ethanol and pH 3.42, matured in oak barrels. These different amounts of PMB and sulphur dioxide corresponded to about 1 mg/l of molecular sulphur dioxide. Our results therefore demonstrate that the control of populations of D. bruxellensis growing in red wine can only be achieved under the presence of relatively high doses of molecular sulphur dioxide

Elimination of trace organics in an MBR/RO system for water reuse

An intensive programme for detection of trace organics was performed in a membrane bioreactor (MBR) plant in Almuñécar (south of Spain) over 1 year. The compounds investigated included 15 pharmaceutically active compounds, 12 polycyclic aromatic hydrocarbons and eight other compounds (nonylphenols, linear alkylbenzene sulphonates and phthalates). The MBR operated with two lines in parallel using a hollow fibre and a flat sheet membrane respectively. Additionally, a reverse osmosis (RO) plant treated the MBR permeate over 1 month and the elimination of trace organics by the MBR/ RO system was assessed. The elimination efficiency of trace organics by the MBR was similar to that found in a conventional activated sludge plant treating the same influent. The concentration of trace organics was reduced after the MBR to a great extent and no significant differences were found between the two lines operating in parallel. The elimination efficiency increased up to 80–100% after passing the RO system. The results indicated that the MBR effluent reached the standard required by the Spanish Royal Decree for Water Reuse and can therefore be reused for multiple purposes, but advanced treatment like RO is necessary when the highest effluent quality is required

Evaluation of draw solutions and commercially available forward osmosis membrane modules for wastewater reclamation at pilot scale

An intensive evaluation of draw solutions (DS) was performed by focusing on the wastewater reuse applications of hybrid forward osmosis (FO) processes. The substances studied were potassium formate, potassium phosphate, magnesium sulphate, sodium chloride, sodium polyacrylate and polyethylene glycol, and their osmotic pressure, conductivity, pH, thermostability, sunlight exposure, toxicity, FO filtration performance and replenishment costs were determined. Additionally, commercially available FO membrane modules were evaluated at pilot scale. The results revealed that the most relevant DS properties for wastewater reuse under the studied conditions were the DS regeneration method, DS replacement price, pH adjustment and toxicity. These properties were shown to be more relevant than filtration flux when a maximum DS osmotic pressure value of 10 bar was used. This was the limit for efficient DS recovery. When the different FO membranes were compared, thin-film composite (TFC) flat-sheet membranes showed the highest flux and the highest salt rejection, and the lowest permeability and salt rejection values were presented by cellulose triacetate (CTA) hollow fibre membranes. Based on the information obtained, a TFC-FO/nanofiltration (NF) demonstration plant will be constructed next to the wastewater treatment plant (WWTP) in San Pedro del Pinatar, in the region of Murcia (Spain). This represents the world's first FO demonstration plant for municipal wastewater reclamation and its results will allow this technology to be evaluated for wastewater reuse for agricultural purpose

Yeasts and wine off-flavours: a technological perspective

Review article. Part of the special issue "Wine microbiology and safety: from the vineyard to the bottle (Microsafety Wine)", 19-20 Nov. 2009, ItalyIn wine production, yeasts have both beneficial and detrimental activities. Saccharomyces cerevisiae is the yeast mainly responsible for turning grape juice into wine but this species and several others may also show undesirable effects in wines. Among such effects, technologists are particularly concerned with the production of offflavours that may occur during all stages of winemaking. Typical spoiling activities include the production of ethyl acetate by apiculate yeasts before fermentation, hydrogen sulphide by S. cerevisiae during fermentation phases, acetaldehyde by film-forming yeasts during bulk storage, and volatile phenols by Dekkera bruxellensis during storage or after bottling. The occurrence of these hazards depends on the technological operations designed to obtain a given type of wine and most can be avoided by current preventive or curative measures. On the contrary, good manufacturing practices must be strengthened to deal with the problem of volatile phenol production in red wines. Appropriate monitoring of D. bruxellensis populations and quantification of 4-ethylphenol is advised during storage, particularly when oak barrels are used, and absence of viable cells must be guaranteed in bottled wines. This work, which is based on our experience at winery level, aims to provide information on appropriate technological strategies to deal with the problem of off-flavours produced by yeasts

Long-term evaluation of a forward osmosis-nanofiltration demonstration plant for wastewater reuse in agriculture

Hybrid forward osmosis (FO) processes such as forward osmosis with membrane bioreactors (FO-MBR), electrodialysis (FO-ED), nanofiltration (FO-NF) or reverse osmosis (FO-RO) present promising technologies for wastewater reuse in agriculture as they meet high effluent quality requirements, especially regarding boron and/or salt content. An FO-NF demonstration plant for this application was built and operated treating 3 m3 h−1 of real wastewater with a salinity of 3-5 mS cm−1 and 1.5 mg L−1 of boron in continuous mode for 480 days. Three draw solutions (DS) were evaluated in different periods of experimentation. Sodium polyacrylate led to reversible fouling on the FO and NF membranes and the permeate was not suitable for irrigation. Magnesium sulphate, used as DS in a second phase, generated severe irreversible fouling on NF membranes and therefore it was discarded. Finally, magnesium chloride showed the best performance, with FO-NF membranes presenting a stable permeability and low membrane fouling during long-term operation. The FO-NF permeate showed high quality for irrigation, achieving a conductivity value of 1 mS cm−1, a boron concentration below 0.4 mg L−1 and an average SAR of 1.98 (mequ L−1)0.5. DS replacement costs were reduced by working with high rejection NF membranes. However, energy consumption costs associated with the NF step make the global process more energy intensive than conventional technology.

Impact of volatile phenols and their precursors on wine quality and control measures of Brettanomyces/Dekkera yeasts

Volatile phenols are aromatic compounds and one of the key molecules responsible for olfactory defects in wine. The yeast genus Brettanomyces is the only major microorganism that has the ability to covert hydroxycinnamic acids into important levels of these compounds, especially 4-ethylphenol and 4-ethylguaiacol, in red wine. When 4-ethylphenols reach concentrations greater than the sensory threshold, all wine’s organoleptic characteristics might be influenced or damaged. The aim of this literature review is to provide a better understanding of the physicochemical, biochemical, and metabolic factors that are related to the levels of p-coumaric acid and volatile phenols in wine. Then, this work summarizes the different methods used for controlling the presence of Brettanomyces in wine and the production of ethylphenols

Perfis de acidos gordos e toxicidade de acidos fracos em leveduras de contaminacao de alimentos

The research carried out in this work concerned the development of a technique for the rapid screening of food contaminating yeasts, based on the analysis of cellular long-chain fatty acid composition, and the evaluation of the effects of several weak carboxylic acids in the physiology of the yeasts Zygosaccharomyces bailii ISA 1307 and Sacchoromycescerevisiae ISA 1000. The developed technique - using the species Saccharomyces cerevisiae, Zygosaccharomyces bailii, Zygosaccharomyces rouxii, Pichia membranaefaciens, Saccharomycodes ludwigii, Schizosaccharomyces pombe, Lodderomyces elogisporus, Brettanomyces/dekkera spp. e Candida spp. - allowed the assessment of the end product contamination sources and demonstrated its interest as a tool in the identification of strains by conventional methodology. In relation to the main physiological aspects of weak carboxylic acids toxicity, the following conclusions were achieved: i) growth and fermentation inhibition mechanisms are not mediate by deficiency in the ammonium or glucose transport induced by benzoic acid, in both strains, ii) in Z.bailii the fermentation inhibition by benzoic acid is not essentially mediated by internal acidification, iii) in Z. bailii the inhibition of fermentation is accompanied by a concomitant decrease in the intracellular ATP levels, unlike in S.cerevisiaeAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1200 Lisboa / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga

Influencia de la comunicaci?n t?cnica en la coordinaci?n de la atenci?n geri?trica durante la crisis del COVID-19 en la provincia de Lugo. Estudio prospectivo

Introducci?n: La pandemia producida por el coronavirus SARS-CoV-2 supone un gran reto sanitario con efectos econ?micos y sociales patentes. La salud de la poblaci?n mundial peligra y las formas habituales de afrontar situaciones epid?micas son puestas en cuesti?n, lo que hace necesario un esfuerzo de coordinaci?n en la atenci?n a las personas mayores. Objetivo: Conocer la influencia que la comunicaci?n t?cnica producida durante la crisis sanitaria generada a ra?z del COVID-19 podr? ejercer sobre la coordinaci?n de la atenci?n geri?trica en la provincia de Lugo. Metodolog?a: Estudio prospectivo Delphi empleando un cuestionario de doble circulaci?n a cumplimentar por expertos en Geriatr?a y Gerontolog?a de la provincia de Lugo constituidos en dos paneles. Resultados: N = 26 (20 mujeres, 6 hombres). Rango de edad: 25 ? 63 a?os. Las respuestas medias de ambos paneles se han aproximado y los rangos se han estrechado en la segunda circulaci?n de la encuesta. Conclusi?n: Una estrategia de comunicaci?n bidireccional entre los profesionales de la Geriatr?a y la Gerontolog?a, basada en documentaci?n t?cnica y cient?fica, facilitar? la coordinaci?n entre niveles asistenciales y mejorar? las expectativas de salud de las personas mayores en situaciones de crisis aunque tambi?n en la cronicidad