Production of bacterial cellulose tubes for biomedical applications: Analysis of the effect of fermentation time on selected properties.

Biosynthesis of bacterial cellulose (BC) in cylindrical oxygen permeable molds allows the production of hollow tubular structures of increasing interest for biomedical applications (artificial blood vessels, ureters, urethra, trachea, esophagus, etc.). In the current contribution a simple set-up is used to obtain BC tubes of predefined dimensions; and the effects of fermentation time on the water holding capacity, nanofibrils network architecture, specific surface area, chemical purity, thermal stability, mechanical properties, and cell adhesion, proliferation and migration of BC tubes are systematically analysed for the first time.

UV Protective, Antioxidant, Antibacterial and Compostable Polylactic Acid Composites Containing Pristine and Chemically Modified Lignin Nanoparticles.

Polylactic acid (PLA) films containing 1 wt % and 3 wt % of lignin nanoparticles (pristine (LNP), chemically modified with citric acid (caLNP) and acetylated (aLNP)) were prepared by extrusion and characterized in terms of their overall performance as food packaging materials. Morphological, mechanical, thermal, UV-Vis barrier, antioxidant and antibacterial properties were assayed; appropriate migration values in food simulants and disintegration in simulated composting conditions were also verified. The results obtained indicated that all lignin nanoparticles succeeded in conferring UV-blocking, antioxidant and antibacterial properties to the PLA films, especially at the higher filler loadings assayed.

Yarrowia lipolytica: a model yeast for citric acid production.

Every year more than 2 million tons of citric acid (CA) are produced around the world for industrial uses. Although initially extracted from citrus, the low profitability of the process and the increasing demand soon stimulated the search for more efficient methods to produce CA. Currently, most world CA demand (99%) is satisfied by fermentations with microorganisms, especially filamentous fungi and yeasts.

Acetylation of bacterial cellulose catalyzed by citric acid: Use of reaction conditions for tailoring the esterification extent.

Bacterial cellulose (BC) nanoribbons were partially acetylated by a simple direct solvent-free route catalyzed by citric acid. The assay of reaction conditions within chosen intervals (i.e.

Facile synthesis of cobalt ferrite nanotubes using bacterial nanocellulose as template.

A facile method for the preparation of cobalt ferrite nanotubes by use of bacterial cellulose nanoribbons as a template is described. The proposed method relays on a simple coprecipitation operation, which is a technique extensively used for the synthesis of nanoparticles (either isolated or as aggregates) but not for the synthesis of nanotubes. The precursors employed in the synthesis are chlorides, and the procedure is carried out at low temperature (90 °C).

Use of grape pomaces to produce biomass of aKomagataella pastoris strain expressing a bovine chymosin activity.

The use of agroindustrial wastes not only decreases bioprocesses and disposal costs but also contributes to the upgrading of the residues. An active recombinant methanol-inducible bovine chymosin has been expressed in our laboratory in the yeastKomagataella pastoris, and grape pomace extracts (GRE) were proposed as a convenient C-energy source for the biomass production of the genetically engineered strain. Carbon and nitrogen sources, growth factors, and initial pH conditions were selected by classical methodology; thereafter, growth conditions optimization was performed using statistical designed experiments (DoEs).

Surface esterification of cellulose nanofibers by a simple organocatalytic methodology.

Bacterial cellulose nanofibers were esterified with two short carboxylic acids by means of a simple and novel organic acid-catalyzed route. The methodology proposed relayed on the use of a non-toxic biobased α-hydroxycarboxylic acid as catalyst, and proceeded under moderate reaction conditions in solventless medium. By varying the esterification interval, acetylated and propionized bacterial cellulose nanofibers with degree of substitution (DS) in the 0.

Statistical optimization of culture conditions for biomass production of probiotic gut-borne Saccharomyces cerevisiae strain able to reduce fumonisin B1.

Aim: To evaluate the ability of probiotic Saccharomyces cerevisiae RC016 strain to reduce fumonisin B(1) (FB(1)) in vitro and to optimize the culture conditions for the growth of the yeast employing surface response methodology.

Methods And Results: Using Plackett-Burman screening designs (PBSD) and central composite designs (CCD), an optimized culture medium containing (g l(-1)) fermentable sugars provided by sugar cane molasses (CMs), yeast extract (YE) and (NH(4))(2) HPO(4) (DAP) was formulated. The S.

Optimization of biomass production of a mutant of Yarrowia lipolytica with an increased lipase activity using raw glycerol.

The yeast Yarrowia lipolytica accumulates oils and is able to produce extracellular lipases when growing in different carbon sources including glycerol, the principal by-product of the biodiesel industry. In this study, biomass production of a novel mutant strain of Y. lipolytica was statistically optimized by Response Surface Methodology in media containing biodiesel-derived glycerol as main carbon source.

Statistical optimization of simple culture conditions to produce biomass of an ochratoxigenic mould biocontrol yeast strain.

Aim:   To maximize biomass production of an ochratoxigenic mould-controlling strain of Lachancea thermotolerans employing response surface methodology (RSM).

Methods And Results:   Using Plackett-Burman screening designs (PBSD) and central composite designs (CCD), an optimized culture medium containing (g l(-1) ): fermentable sugars (FS), 139·2, provided by sugar cane molasses (CMz), (NH(4) )(2) HPO(4) (DAP), 9·0, and yeast extract (YE), 2·5, was formulated. Maximal cell concentration obtained after 24 h at 28°C was 24·2 g l(-1) cell dry weight (CDW).

[Studies of viability and vitality after freezing of the probiotic yeast Saccharomyces boulardii: physiological preconditioning effect].

The aim of this study was to evaluate the vitality and viability of the probiotic yeast Saccharomyces boulardii after freezing/thawing and the physiological preconditioning effect on these properties. The results indicate that the specific growth rate (0.3/h(-1)) and biomass (2-3 x10(8)cells/ml) of S.

Exploring the use of natural antimicrobial agents and pulsed electric fields to control spoilage bacteria during a beer production process.

Different natural antimicrobials affected viability of bacterial contaminants isolated at critical steps during a beer production process. In the presence of 1 mg/ml chitosan and 0.3 mg/ml hops, the viability of Escherichia coli in an all malt barley extract wort could be reduced to 0.

Modelling the freezing response of baker's yeast prestressed cells: a statistical approach.

Aims: To study the effect of prestress conditions on the freezing and thawing (FT) response of two baker's yeast strains and the use of statistical analysis to optimize resistance to freezing.

Methods And Results: Tolerance to FT of industrial strains of Saccharomyces cerevisiae was associated to their osmosensitivity and growth phase. Pretreatments with sublethal stresses [40 degrees C, 0.

[Increase of rising activity of commercial yeasts by application of stress conditions during their propagation].

Rising activity determined as CO2 production of two commercial strains of Saccharomyces cerevisiae could be increased mainly in sweet bread doughs by introducing a "starvation/pulse feeding" schedule of sugar cane molasses during a fed-batch propagation. Such increase was strain dependent. Except for the trehalose intracellular level, other traits related to the yeast industrial performance were unaffected.

Selective antimicrobial activity of chitosan on beer spoilage bacteria and brewing yeasts.

Chitosan (0.1 g l(-1)), assayed in a simple medium, reduced the viability of four lactic acid bacteria isolated during the beer production process by 5 logarithmic cycles, whereas activity against seven commercial brewing yeasts required up to 1 g chitosan l(-1). Antimicrobial activity was inversely affected by the pH of the assay medium.

[Optimization of the conditions for electroporation and the addition nisin for Pseudomonas aeruginosa inhibition].

A mathematical approach was applied in order to optimize the effect of electroporation by application of pulsed electric fields (PEF) and nisin addition on the inhibition of a strain of Pseudomonas aeruginosa isolated from river sediments. This strain showed to be highly resistant to nisin as only two log cycles reduction of viable cells were obtained in the presence of 84,000 IU/ml nisin. But when a combination of bacteriocin and selected PEF treatment conditions were applied, 4.

Inactivation of Escherichia coli by a combination of nisin, pulsed electric fields, and water activity reduction by sodium chloride.

The effect of nisin combined with pulsed electric fields (PEF) and water activity reduction by sodium chloride (NaCl) on the inactivation of E. coli in simulated milk ultrafiltrate media was studied with a Doehlert design and a response surface method. The reduction of water activity from 0.

Combined effect of water activity and pH on the inhibition of Escherichia coli by nisin.

The Doehlert design and surface response methodology were used to study the influence of pH and water activity (aw) on Escherichia coli inhibition by nisin. Combining stress factors at levels where they are not inhibitory by themselves, a reduction of E. coli survival fraction can be achieved with lower nisin doses than in a single nisin treatment.

Commercial baker's yeast stability as affected by intracellular content of trehalose, dehydration procedure and the physical properties of external matrices.

The effects of vacuum-drying and freeze-drying on the cell viability of a commercial baker's yeast, Saccharomyces cerevisiae, strain with different endogenous contents of trehalose were analyzed. An osmotolerant Zygosaccharomyces rouxii strain was used for comparative purposes. Higher viability values were observed in cells after vacuum-drying than after freeze-drying.

[Inhibition of Bacillus coagulans growth in laboratory media and in fruit purees].

The growth of two strains of B. coagulans was inhibited in laboratory media at pH < or = 4.5, and at water activity (aw) levels of 0.

Combined effect of nisin and pulsed electric fields on the inactivation of Escherichia coli.

The Doehlert design was applied in order to investigate the combined effect of nisin and high voltage pulsed electric fields (PEF) on the inactivation of Escherichia coli in simulated milk ultrafiltrate media. Nisin alone was totally inactivated by PEF, but in the presence of bacterial cells a protective effect was observed. However, the effectiveness of nisin was still decreased when bacterial cells were subjected to the combined treatment.

Inhibitory effects of vanillin on some food spoilage yeasts in laboratory media and fruit purées.

The effect of vanillin and essential oil of mint on the growth of different strains of food spoilage yeasts in laboratory media and fruit purées was studied. Growth of Saccharomyces cerevisiae, Zygosaccharomyces rouxii, Debaryomyces hansenii and Z. bailii was inhibited in culture media and apple purée containing 2000 ppm of vanillin for 40 days storage at 27 degrees C and a(w) 0.