Natural antimicrobial systems protected by complex polyhydroxyalkanoate matrices for food biopackaging applications - A review.

Interest is growing in entrapping natural antimicrobial compounds (NACs) within polyhydroxyalkanoates (PHAs) to produce active food-biopackaging systems. PHAs are versatile polymeric macromolecules that can protect NAC activity by entrapment. This work reviews 75 original papers and 18 patents published in the last 11 years concerning PHAs as matrices for NACs to summarize the physicochemical properties, release, and antimicrobial activities of systems fabricated from PHAs and NACs (PHA/NAC systems). PHA/NAC systems have recently been used as active food biopackaging systems to inactivate foodborne pathogens and prolong food shelf life. PHAs protect NACs by increasing the degradation temperature of some NACs and decreasing their loss of mass when heated. Some NACs also transform the PHA/NAC systems into more thermostable, flexible, and resistant when interacting with PHAs while also improving the barrier properties of the systems. NAC release and activity are also prolonged when NACs are trapped within PHAs. PHA/NAC systems, therefore, represent ecologically friendly materials with promising applications.

Films of biopolymers, pectin and gellan, enriched with natamycin and clove essential oils for the packaging of Corn tortilla: Protection against Staphylococcus aureus and Candida parapsilosis.

It was investigated the microbial protection of corn tortilla, traditional Mexican food with high acceptance, for food safety. We elaborated a functional film (FF) prepared with 0.4% (w/v) gellan gum, 2% (w/v) citrus pectin, 0.5% (w/v) glycerol, 0.0003% (w/v) natamycin, 0.03% (v/v) essential clove oils, and 0.1% (v/v) tween 80. The FF impeded the growth of indicator microorganisms in corn tortilla medium: Staphylococcus aureus (i.e., 35 °C, 50% RH, 7 days) and Candida parapsilosis (i.e., 27 °C, 42% RH, 7 days; and 9 °C, 95% RH, 30 days). In packaged artisanal corn tortilla storage at 22 °C and 50% RH for 30 days, the FF-treatments showed 5.5 log CFU/g total aerobes and 4.8 log CFU/g yeasts and moulds, being two and three logs lower than the concentrations recorded in the controls with no film, respectively. Some physical-mechanical properties of FF were Young's modulus, 500 MPa; elongation at break, 10%; stress at break, 18.5 MPa; oxygen permeability, 4 × 10-13 g m Pa-1 s-1 m-2; and water vapour permeability, 4.8 × 10-11 g m Pa-1 s-1 m-2. Also, the sensory evaluation of wrapped tortilla suggested no negative effects. The obtained results envisage potential food-packaging applications with the elaborated films.

Bacteriocins Produced by LAB Isolated from Cheeses within the Period 2009-2021: a Review.

A survey is presented concerning original research articles published in well-reputed scientific journals on the isolation of lactic acid bacteria (LAB) from cheeses worldwide, where researchers evaluated the bacteriocin production by such isolates in searching for novel functional peptides that can exhibit potential for biotechnological applications. Seventy-one articles were published in the period of study, with contributions being American (45%), Asiatic (28%), and European (21%), being Brazil-USA-Mexico, Turkey-China, and France-Italy the countries that contributed the most for each said continent, respectively. Most of the isolated LAB belong to the genera Enterococcus (35%), Lactobacillus (30%), Lactococcus (14%), and Pediococcus (10%), coming from soft (64%), hard (27%), and semi-hard (9%) cheeses, predominantly. Also, scholars focused mainly on the food biopreservation (81%) and pharmaceutical field (18%) potential applications.

Pectin-gellan films intended for active food packaging: release kinetics of nisin and physico-mechanical characterization.

Films were prepared by casting 2% w/v apple pectin, 0.5% w/v low-acyl gellan and 2.2% w/v glycerol as plasticizer. Bioactive film (BF, films with 3912 International Units (IU) nisin/cm2) and control films (CF, films without nisin) were elaborated. The objective was to analyze the release kinetics of nisin from films to a food model, to determine the period of film bioactivity and potential use as antimicrobial packaging. The release of nisin from BF to a food model was determined at 5 °C and 30 °C. The release kinetics of nisin was fitted to the analytical solution of the Fick's second law for an infinite plate. The diffusion coefficients of nisin (D) were 5.22 × 10-14 and 7.36 × 10-14 m2/s for 5 °C and 30 °C, respectively. Besides, both films were characterized in their mechanical properties and gas permeabilities [oxygen (PO2) and water vapour permeability (WVP)]. The mechanical properties were reduced by the nisin incorporation, whereas PO2 was increased, and no significant effect on WVP was observed.

A review of extracellular polysaccharides from extreme niches: An emerging natural source for the biotechnology. From the adverse to diverse!

Every year, new organisms that survive and colonize adverse environments are discovered and isolated. Those organisms, called extremophiles, are distributed throughout the world, both in aquatic and terrestrial environments, such as sulfurous marsh waters, hydrothermal springs, deep waters, volcanos, terrestrial hot springs, marine saltern, salt lakes, among others. According to the ecosystem inhabiting, extremophiles are categorized as thermophiles, psychrophiles, halophiles, acidophiles, alkalophilic, piezophiles, saccharophiles, metallophiles and polyextremophiles. They have developed chemical adaptation strategies that allow them to maintain their cellular integrity, altering physiology or improving repair capabilities; one of them is the biosynthesis of extracellular polysaccharides (EPS), which constitute a slime and hydrated matrix that keep the cells embedded, protecting from environmental stress (desiccation, salinity, temperature, radiation). EPS have gained interest; they are explored by their unique properties such as structural complexity, biodegradability, biological activities, and biocompatibility. Here, we present a review concerning the biosynthesis, characterization, and potential EPS applications produced by extremophile microorganisms, namely, thermophiles, halophiles, and psychrophiles. A bibliometric analysis was conducted, considering research articles published within the last two decades. Besides, an overview of the culture conditions used for extremophiles, the main properties and multiple potential applications of their EPS is also presented.

Toward understanding the signals of bacteriocin production by Streptococcus spp. and their importance in current applications.

Microorganisms have developed quorum sensing (QS) systems to detect small signaling molecules that help to control access to additional nutrients and space in highly competitive polymicrobial niches. Many bacterial processes are QS-regulated; two examples are the highly related traits of the natural genetic competence state and the production of antimicrobial peptides such as bacteriocins. The Streptococcus genus is widely studied for its competence and for its ability to produce bacteriocins, as these antimicrobial peptides have significant potential in the treatment of infections caused by multiple-resistant pathogens, a severe public health issue. The transduction of a two-component system controls competence in streptococci: (1) ComD/E, which controls the competence in the Mitis and Anginosus groups, and (2) ComR/S, which performs the same function in the Bovis, Mutans, Salivarius, and Pyogenic groups. The cell-to-cell communication required for bacteriocin production in the Streptococcus groups is controlled mainly by a paralog of the ComD/E system. The relationships between pheromone signals and induction pathways are related to the bacteriocin production systems. In this review, we discuss the recent advances in the understanding of signaling and the induction of bacteriocin biosynthesis by QS regulation in streptococci. This information could aid in the design of better methods for the development and production of these antimicrobial peptides. It could also contribute to the analysis and emerging applications of bacteriocins in terms of their safety, quality, and human health benefits.

Physicochemical characterization and emulsifying properties of a novel exopolysaccharide produced by haloarchaeon Haloferax mucosum.

The physicochemical characterization and emulsifying functional properties of a novel exopolysaccharide (EPS) produced by haloarchaea Haloferax mucosum (DSM 27191) were investigated. This biopolymer has a high molecular weight of 152 kDa and important protein content of 10%. Different culture media compositions were investigated taking the ATCC 2185 medium as a base and supplementing with varying concentrations of yeast extract and glucose or sucrose as carbon sources to produce the EPS in a liquid medium. The highest EPS production (7.15 ±â€¯0.44 g/L) was obtained at 96 h. EPS aqueous dispersions showed a non-Newtonian rheological behavior which was well fitted to the Cross equation. The EPS (at 0.32% w/w) was capable of stabilizing water-in-oil emulsions with different nonpolar solvents, including n-hexane, kerosene, chloroform, castor oil and mineral oil. EPS retained its emulsifying activity after to be incubated for one hour in a wide range of temperatures (25, 40, 70 and 100 °C), pH (4, 6.5, 7 and 12) and NaCl concentrations (0, 2.0 and 4.0 M). The viscoelastic behavior and stability of hexane-in-water emulsion were examined through oscillatory shear measurements.

Bacteriocin encapsulation for food and pharmaceutical applications: advances in the past 20 years.

The encapsulation of bacteriocins from lactic acid bacteria has involved several methods to protect them from unfavourable environmental conditions and incompatibilities. This review encompasses different methods for the encapsulation of bacteriocins and their applications in both food and pharmaceutical fields. Based on the bibliometric analysis of publications from well-reputed journals including different available patents during the period from 1996 to 2017, 135 articles and 60 patents were collected. Continent-wise contributions to the bacteriocins encapsulation research were carried out by America (52%), Asia (29%) and Europe (19%); with the United States of America, Brazil, Thailand and Italy the countries with major contributions. Till date, different methods proposed for encapsulation have been (i) Film coatings (50%), (ii) Liposomes (23%), (iii) Nanofibers (22%) and (iv) Nanoparticles (4%). Bacteriocins encapsulation methods frequently carried out in food protection (70%); while in the pharmaceutical field, 30% of the research was conducted on multi drug resistant therapy.

Modelling the effect of temperature on the water sorption isotherms of chitosan films

Abstract The interaction of the water molecules from the environment with foods and other materials can be evaluated using sorption isotherms. Films and biodegradable films are susceptible to changes in their functional characteristics due to adsorbed water. The amount of moisture that biodegradable films can adsorb depends on the temperature, relative humidity of the storage area and chemical composition. Several mathematical models can be used to describe the behavior of sorption isotherms in biodegradable films and some of them have been modified to include the temperature parameter into the equation. In this research, the original and modified BET, GAB, Halsey, Henderson and Oswin models were assessed to determine their suitability describing the behavior of moisture adsorption isotherms of chitosan films at 15, 20, 25 and 30 °C. The modified models of GAB, Oswin and Halsey gave the best fit to the experimental sorption data of the chitosan films, with R2 values higher than 0.97 demonstrating that those models describe better the sorption isotherms at the temperatures studied.

Effect of equilibrium moisture content on barrier, mechanical and thermal properties of chitosan films.

Water molecules modify the properties of biodegradable films obtained from hydrophilic materials. Most studies dealing with thermal, mechanical and barrier properties of hydrophilic films are carried out under one relative humidity (RH) condition. The objective of this work was to evaluate the effect of the moisture content on the thermal, mechanical and barrier properties of chitosan films under several RH conditions. Microclimates, obtained with saturated salt solutions were used for conditioning samples and the properties of the films were evaluated under each RH condition. Chitosan films absorbed up to 40% of moisture at the higher RH studied. The percentage of elongation and the water vapour permeability increased while tensile strength, Young's modulus and glass transition temperature decreased, when the moisture content increased. The results suggest that the water molecules plasticized the polymer matrix, changing the properties when the films were in contact with high RH environments.

Kinetics of infective juvenile production of the entomopathogenic nematode Steinernema carpocapsae in submerged monoxenic culture.

The effects of culture medium formulations on the kinetics of infective juvenile (IJ) production of the entomopathogenic nematode Steinernema carpocapsae in submerged monoxenic culture, were studied at the cylindrical-bottle scale using six culture media containing agave juice from Agave spp. among other ingredients. The IJ production kinetics was well modelled through a re-parameterised 3-parameter Gompertz model with kinetic parameters: IJ-lag phase lambda (IJ) (day), maximum IJ-stage production rate m (max )(day(-1)), and IJ-multiplication factor (C (IJ)/C (IJ,0))(max)(-). The variation of lambda (IJ) was not very important within fermentations (10.3-16.2 days); nonetheless, important effects were observed on m (max) (32.8-241.2 days(-1)) and (C (IJ)/C (IJ,0))(max) (66(-) to 611.4(-)). Particularly, maximum values of m (max) and (C (IJ)/C (IJ,0))(max) were obtained in medium A4 (0.276 l l(-1) agave juice, 17 g l(-1) yeast extract, 12 g l(-1) dried egg yolk, 0.025 l l(-1) corn oil). Also, the maximum IJ concentration (249,444 per ml) was achieved in A4-fermentations.

Submerged monoxenic culture of the entomopathogenic nematode Steinernema carpocapsae in an internal-loop airlift bioreactor using two configurations of the inner tube.

This article reports the submerged culture of the entomopathogenic nematode Steinernema carpocapsae and its symbiotic bacterium, Xenorhabdus nematophila, within an internal-loop airlift bioreactor. Two configurations of the inner cylinder were tested: a standard draft tube (SDT) and a static mixer (SM), as well as two production media: MP1 (500 mL/L whey, among other ingredients) and MP2 (82 mL/L agave-juice from Agave spp., among other ingredients). Three fermentations were carried out: F1 --> SDT-MP1, F2 --> SM-MP1 and F3 --> SM-MP2. The operating conditions were expressed on the basis of dimensionless Reynolds number (Re) and volumetric oxygen transfer coefficient (k(L)a), both of them determined on riser and downcomer sections within the bioreactor. The experiments began with fewer than 1,000 infective juvenile nematode stages (IJ) per mL and at t = 20 d, they achieved (nematodes/mL-%IJ) 222,000-87%, 62,200-23% and 114,600-80%, within F1, F2 and F3 experiments, respectively. Nonetheless, the achieved maximum nematode biomass concentrations (g/L) were F1 --> 408, F2 --> 557 and F3 --> 613, and occurred at t = 16, 10 and 12 d, respectively. The fermentation operating conditions involved 0.042 (-) < Re < 647 (-) and 2.8 x 10(-4) s(-1) < k(L)a < 0.0447 s(-1), as functions of 0.004 m/s < superficial gas velocity (within the riser) < 0.079 m/s, 0.001 m/s < mean downcomer velocity < 0.014 m/s, and culture broth rheological properties which evolved from nearly the Newtonian behaviour to the pseudoplastic one. The maximum IJ concentration was achieved within F1 experiment (193,406 IJ/mL). Also, fermentation conditions involving higher riser-Re and lower downcomer-Re as well as higher nutriment concentrations in culture medium, promote higher nematode biomass concentrations but lower %IJ, maybe as a result of better conditions for the nematode population development.

Monoxenic liquid culture of the entomopathogenic nematode Steinernema carpocapsae using a culture medium containing whey kinetics and modeling.

The submerged culture of the entomopathogenic nematode Steinernema carpocapsae and its symbiotic bacterium, Xenorhabdus nematophila, was carried out in orbitally agitated bottles using a culture medium containing whey (in grams per litre: 500 whey, 20 yeast extract, 10 dried egg yolk-food grade, 3 sodium chloride, 37 corn oil-food grade). Maximum total viable nematode concentrations of 198,333ml(-1) were achieved within fermentations of 24 days with 64% of the nematode population within the infective juvenile stage (IJ) (126,666ml(-1)) at the end. The kinetics of the bioprocess was well modelled using the four-parameter Sigmoidal model and the corresponding maximum specific rates of nematode production (0.47 day(-1)), carbohydrates consumption (0.0008g(carbohydrates)g(nematodes)(-1)day(-1)) and nitrogen consumption (4.44g(nitrogen)g(nematodes)(-1)day(-1)) are first proposed. Besides, X. nematophila appears to have the capacity of lactose hydrolysis.

Monoxenic production of the entomopathogenic nematode Steinernema carpocapsae using culture media containing agave juice (aguamiel) from Mexican maguey-pulquero (Agave spp). Effects of the contents of nitrogen, carbohydrates and fat on infective juvenile production.

The production of infective juvenile stages (IJ) of the entomopathogenic nematode Steinernema carpocapsae in the presence of its symbiotic bacterium Xenorhabdus nematophilus was carried out in orbitally agitated bottles. Four complex culture media (M1-M4) were used, containing from 8% to 28% (by vol.) agave juice (aguamiel) from Mexican maguey-pulquero (Agave spp) as the main carbohydrate source. After 20 days of fermentation, a maximum viable IJ concentration of 249,000 IJ/ml and an initial nematode population multiplication factor of x620 were achieved when medium M4 was used (aguamiel concentration in this medium was 28% by vol.). M4 medium contained (w/v): 0.3% total nitrogen, 3.2% total carbohydrates and 3.0% total fat. According to the results obtained, total carbohydrates concentration appeared to be of great importance in obtaining high IJ concentrations.

Evolution of culture broth rheological properties during propagation of the entomopathogenic nematode Steinernema carpocapsae, in submerged monoxenic culture.

This article presents the evolution of culture broth rheological properties during monoxenic cultures of Steinernema carpocapsae in cylindrical bottles agitated orbitally. Rheological properties were evaluated in simple-shear flow conditions and were well-modeled by the Ostwald-de Waele model. Rheological properties varied from slightly dilatant, n = 1.2 (-), to moderately pseudoplastic flow behavior, n = 0.6 (-). Nematode concentrations increased from 750 +/- 190 to 130 900 +/- 6900 nematodes/mL, and the apparent viscosity (eta(a)) evolved from 4.5 +/- 0.7 to 46.6 +/- 3.2 mPa.s during the fermentations. Rheological behavior did not appear to be strongly influenced by nematode number and/or its stage of development; however, the release of substances from the decomposition of nematode cadavers appeared to be of great importance. Among the different developmental stages of the nematodes, only juveniles of the first stage (J1) were highly susceptible to the shearing conditions tested (shear stress, tau(r)()(theta), from 0.9 to 3.5 Pa during periods of 80-100 min), resulting in the viability loss of 85% of J1 nematodes.