Carmen Sieiro

Production of higher alcohols, ethyl acetate, acetaldehyde and other compounds by 14Saccharomyces cerevisiae wine strains isolated from the same region (Salnés, N.W. Spain)

Fourteen strains of the yeastSaccharomyces cerevisiae were isolated from three wineries in the Salnés wine region (N.W. Spain) at the three different periods of the natural fermentation. Each wild yeast was screened for production of acetaldehyde, ethyl acetate, isobutanol,n-propanol, amylic alcohol and other important enological compounds during laboratory scale fermentations of grape juice. After 25 days at 20°C, the analytical results evidenced variations in the production of acetaldehyde (from 13.1 to 24.3 mg/l), isobutanol (from 27.7 to 51.1 mg/l), amyl alcohols (from 111 to 183 mg/l) and ethyl acetate (from 19.3 to 43.7 mg/l). Although isolated from the same wine region, differences in the wine composition were observed depending on the particular yeast strain used for the vinification experiments.

Chitosan and silver nanoparticles as pudding with raisins with antimicrobial properties

Chitosan nanoparticles (CS-NP) containing small silver nanoparticles are reported (Ag@CS-NP). CS-NP was synthesized using tripolyphosphate (TPP) as a polyanionic template. TPP also served to electrostatically attract Ag(+) inside CS-NP, where it was reduced by the terminal glucosamine units of the biopolymer. This procedure is environmental friendly, inexpensive, and permits the synthesis of very small AgNP (0.93-1.7 nm), with only a discrete dependence from the amount of silver nitrate used (5-200mg). The obtained hybrid nanocomposites Ag@CS-NP were characterized by DLS, HRTEM, and HAADF-STEM presenting a mean hydrodynamic diameter of 78 nm. The antimicrobial activity of Ag@CS-NP against Candida glabrata, Sacharomyces cerevisiae, Escherichia coli, Klebsiella pneumoniae, Salmonella, Staphylococcus aureus, and Bacillus cereus corresponded to MIC values lower than for AgNO(3).

Contribution by Saccharomyces cerevisiae yeast to fermentative flavour compounds in wines from cv. Albariño

A comparative study was made of the fermentation products of Spanish Albariño wines produced with spontaneous yeast flora and an indigenous selected Saccharomyces cerevisiae strain (Alb16). The content of fermentative volatile compounds was determined by gas-chromatography-FID. Fifteen compounds (5 alcohols, 7 esters and 3 acetates) were identified in the two Albariño wines studied. Higher alcohols, ethyl esters (except ethyl hexanoate and ethyl octanoate) and acetates were in greater concentration in the spontaneous fermentation wine than in that with selected Alb16 strain. Principal components analysis showed good separation between the different wines.

Use of a PGU1 recombinant Saccharomyces cerevisiae strain in oenological fermentations

Aim: The aim of this work was the construction of an oenological Saccharomyces cerevisiae strain able to overexpress the PGU1 gene in order to be used in trial fermentations.

Genetic determination of polygalacturonase production in wild-type and laboratory strains of Saccharomyces cerevisiae

Abstract The genetic determination of polygalacturonase (PG) production in Saccharomyces cerevisiae was studied by biochemical and classical genetic techniques. Crosses of PG+ strains with PG– strains showed that in the haploid wild-type-derived strain, two structural genes were involved in the production of a hydrolysis halo on plates with polygalacturonic acid. However, in the case of PG+ laboratory strain IM1-8b, the phenotype was controlled by only one structural gene although the analysis of PG– IM1-8b mutants demonstrated the existence of at least two complementation groups. All these genetic results were assessed biochemically by means of cation-exchange chromatography. Two enzymes were separated in the wild-type strain, and only one in the laboratory strain. The three enzymes had different Km values, molecular masses, and optimal pHs for activity.

Characterization of a broad pH range protease of Candida caseinolytica

Aims: The study of a protease secreted by Candida caseinolytica for use in future industrial applications.

Grape Juice Biodegradation by Polygalacturonases from Saccharomyces cerevisiae

Abstract Some strains of S. cerevisiae capable of degrading pectic susbstances were selected in order to determine their effect on must biodegradation and, in particular, on the clarification processes. The pectolytic activity in these yeasts was always lower than in filamentous fungi and certain bacteria. The effect of pectinases from these three biotic groups, as far as the viscosity was concerned, was not appreciable in either case; however, a relevant effect, caused by enzymes from yeasts, on filtration time was found. With strains 1389 and C6, the filtration time was reduced by about 50%. It is concluded that biodeterioration of must/wine may be caused by an excess of yeast polygalacturonases originating during primary fermentation from the unappropriate S. cerevisiae strain giving rise to thin lines.

Microbial Pectic Enzymes in the Food and Wine Industry

Pectins are polysaccharides ubiquitous in the plant kingdom and constitute the major component of plant cell walls. The pectinases are a group of related enzymes capable of degrading pectin. Therefore, this group of enzymes have been used for decades in the food and winemaking industry for the processing of fruit juices (Mohnen, 2008; Prade et al., 1999; Ribeiro et al., 2010). The pectinases are synthesized by plants and microorganisms, the latter being used for industrial production. Microorganisms are used to produce many enzymes of industrial interest in processes relatively inexpensive and environmentally friendly. Moreover, enzymatic catalysis is preferred over other chemical methods since it is more specific, less aggressive and generates less toxicity (Hoondal et al., 2002; Lara-Marquez et al., 2011). Advances in biotechnology, especially in the fields of molecular biology and microbial genetics, have led to major advances in enzyme technology and have allowed, in many cases, the development of new producing strains and microbial enzymes. The production of pectinases may also benefit from these technologies. This article reviews the characteristics of pectic substances, the types and mode of action of enzymes which degrade them and the main applications of commercial preparations of microbial pectinases in the food and winemaking industry, followed by a review of new microorganisms and pectolytic enzymes, evaluating new approaches to their production, marketing and use.

Cloning and Expression of clt Genes Encoding Milk-Clotting Proteases from Myxococcus xanthus 422

ABSTRACT The screening of a gene library of the milk-clotting strain Myxococcus xanthus 422 constructed in Escherichia coli allowed the description of eight positive clones containing 26 open reading frames. Only three of them (cltA, cltB, and cltC) encoded proteins that exhibited intracellular milk-clotting ability in E. coli, Saccharomyces cerevisiae, and Pichia pastoris expression systems.

Production and partial characterization of a β‐amylase by Xanthophyllomyces dendrorhous

Aims: The characterization of a β‐amylase produced by Xanthophyllomyces dendrorhous.