Study on application of biocellulose-based material for cheese packaging

Bacterial cellulose (BC, biocellulose) is a natural polymer of microbiological origin that meets the criteria of a biomaterial for food packaging. The aim of the research was to obtain biocellulose and test its chemical as well as physical characterization as a potential packaging for Dutch-type cheeses. Four variants of biocellulose-based material were obtained: not grinded and grinded variants obtained from YPM medium (YPM-BCNG and YPM-BCG, respectively) and not grinded and grinded variants from acid whey (AW) (AW-BCNG and AW-BCG, respectively). It was demonstrated that AW-BCNG exhibited the highest thermostability and the highest degradation temperature (348 °C). YPM-BCG and YPM-BCNG demonstrated higher sorption properties (approx. 40 %) compared to AW-BCG and AW-BCNG (approx. 15 %). Cheese packaged in biocellulose (except for YPM-BCNG) did not differ in water, fat, or protein content compared to the control cheese. All of the biocellulose packaging variants provided the cheeses with protection against unfavourable microflora. It was demonstrated that cheeses packaged in biocellulose were characterized by lower hardness, fracturability, gumminess, and chewiness than the control cheese sample. The results obtained indicate that BC may be a suitable packaging material for ripening cheeses, which shows a positive impact on selected product features.

The Genotyping Diversity and Hemolytic Activity of Cronobacter spp. Isolated from Plant-Based Food Products in Poland

The present study aimed to determine the genotyping diversity and hemolytic properties of 24 strains of Cronobacter spp. (15 Cronobacter sakazakii, 6 Cronobacter malonaticus, 2 Cronobacter turicensis, and 1 Cronobacter condimenti) isolated from commercial ready-to-eat leaf vegetables, sprouts, nuts, and dried fruits. The multilocus sequence typing (MLST) method was used to determine the sequence types (ST) and clonal complexes (CC) of these strains. The study demonstrated the high genotypic diversity of the Cronobacter genus bacteria isolated from plant-based foods. Five novel sequence types (804, 805, 806, 807, and 808) and the presence of novel alleles in the ppsA, gltB, gyrB, and infB loci were detected. In total, 16 of the 24 strains were assigned to the sequence types ST99, ST258, ST17, ST648, ST21, ST494, and ST98. One C. sakazakii strain (s12) isolated from alfalfa sprouts was assigned to the clonal complex CC4, which encompasses strains often associated with severe infections leading to meningitis in infants. In addition, 87.5% and 16.7% of the Cronobacter spp. strains showed β-hemolysis of equine and sheep red blood cells, respectively. The presence of the pathogenic species C. sakazakii, C. malonaticus, and C. turicensis in ready-to-eat plant-derived food products shows they are potential sources of infection, especially to those with compromised immunity, which substantiates their further multi-faceted characterization. The significance of this study may prove useful not only in epidemiological investigations, but also in assessing the risk of infections caused by the presence of Cronobacter.

The Impact of White Mulberry, Green Barley, Chia Seeds, and Spirulina on Physicochemical Characteristics, Texture, and Sensory Quality of Processed Cheeses

Processed cheeses (PC) are products resulting from the mixing and melting of rennet cheese, emulsifying salts, water, and possibly various additional ingredients. They are considered good vehicles for new ingredients, including plant-based ones. In addition to the health-promoting effects of plant-based ingredients, some of them can also affect positively the quality characteristics of PC (e.g., texture, taste, and consistency) and their addition may reduce the amount of emulsifying salts used. The aim of the study was to determine the possibility of the addition of 0.5, 1.0, 2.0, and 3.0% white mulberry (M), chia (Ch), green barley (GB), or spirulina (S) to PC and the effects on selected characteristics of these products (chemical composition, pH, water activity, color parameters, texture, and sensory properties). In all PC variants, a significance decrease in the dry matter content was observed with an increase in the additive level. The use of plant-based additives allowed us to reduce the addition of emulsifying salts by 50% compared to their typical amounts and the share of rennet cheese in the PC recipe by approximately 18%, which had a beneficial effect on the nutritional value of these products. The use of 3% GB, Ch, or M as additives to PC enabled a reduction in its sodium content by 27, 27, and 42%, respectively, compared to the control cheese. Among the tested additives, GB caused the greatest increase in the hardness of PC (even at the amount of 0.5%), indicating that is beneficial and can be used in the production of sliced PC. All the additives either significantly reduced the adhesiveness of PC or had no effect on this parameter. In terms of sensory characteristics, the highest acceptable addition of GB was 0.5%, and that for S and Ch was 1%, while the addition of M, even at 3%, was assessed very positively. The results of this research may be helpful in the development of new recipes for processed cheeses obtained in industrial conditions.

The Presence of Plasmids in Lactococcus lactis IL594 Determines Changes in the Host Phenotype and Expression of Chromosomal Genes

The L. lactis IL594 strain contains seven plasmids (pIL1 to pIL7) and is the parental strain of the plasmid-free L. lactis IL1403, one of the most studied lactic acid bacteria (LAB) strain. The genetic sequences of pIL1 to pIL7 plasmids have been recently described, however the knowledge of global changes in host phenotype and transcriptome remains poor. In the present study, global phenotypic analyses were combined with transcriptomic studies to evaluate a potential influence of plasmidic genes on overall gene expression in industrially important L. lactis strains. High-throughput screening of phenotypes differences revealed pronounced phenotypic differences in favor of IL594 during the metabolism of some C-sources, including lactose and β-glucosides. A plasmids-bearing strain presented increased resistance to unfavorable growth conditions, including the presence of heavy metal ions and antimicrobial compounds. Global comparative transcriptomic study of L. lactis strains revealed variation in the expression of over 370 of chromosomal genes caused by plasmids presence. The general trend presented upregulated energy metabolism and biosynthetic genes, differentially expressed regulators, prophages and cell resistance proteins. Our findings suggest that plasmids maintenance leads to significant perturbation in global gene regulation that provides change in central metabolic pathways and adaptive properties of the IL594 cells.

The Impact of the Adjunct Heat-Treated Starter Culture and Lb. helveticus LH-B01 on the Proteolysis and ACE Inhibitory Activity in Dutch-Type Cheese Model during Ripening

Simple Summary

Adjunct cultures are used in cheesemaking to improve flavour characteristics and accelerating cheese ripening. Different adjunct cultures are capable of producing enzymes with the specificity to hydrolyze caseins, leading to the release of various bioactive compounds. We studied the effect of adjunct heat-treated starter XT–312 and a cheese culture Lb. helveticus LH-B01 on selected physicochemical, microbiological properties, and on proteolysis in cheese models. Additionally, the effect of adjunct cultures on ACE inhibitory activity during ripening was determined. The application of adjunct cultures may be used as functional ingredients in Dutch-type cheese to maintain sufficient bioactive properties and improve proteolysis.

Abstract

Adjunct cultures are used in cheesemaking to improve the sensory characteristics of the ripened cheeses. In addition, it is known that different adjunct cultures are capable of producing enzymes with the specificity to hydrolyze caseins, leading to the release of various bioactive compounds (bioactive peptides, amino acids, etc.). The objective of this study was to evaluate the effect of adjunct heat-treated starter XT–312 and a cheese culture Lb. helveticus LH-B01 on the proteolytic activity and angiotensin converting enzymes inhibitors (ACE) in cheese models during ripening. Seven different cheese models were evaluated for: proteolytic activity using the spectrophotometric method with ortho-phthaldialdehyde (OPA), soluble nitrogen (SN), trichloroacetic acid-soluble nitrogen (TCA-SN) phosphotungstic acid-soluble nitrogen (PTA-SN), total nitrogen (TN), pH, contents of water, fat, as well as for total bacteria count (TBC), count of Lactococcus genus bacteria, count of Lb. helveticus, and number of non-starter lactic acid bacteria (NSLAB). Presence of adjunct bacterial cultures both in the form of a cheese culture LH-B01 and heat-treated XT–312 starter promoted primary and secondary proteolysis, which resulted in acceleration of the ripening process. ACE inhibitory activity and proteolytic activity was the highest throughout of ripening for cheese model with LH-B01 culture. The cheese models with the adjunct heat-treated starter were characterized by lower TBC, NSLAB and lower count of Lactococcus genus bacteria during ripening, compared to control cheeses.

Modeling of Osmotic Dehydration of Apples in Sugar Alcohols and Dihydroxyacetone (DHA) Solutions

The purpose of this paper is twofold: on the one hand, we verify effectiveness of alternatives solutes to sucrose solution as osmotic agents, while on the other hand we intend to analyze modeling transfer parameters, using different models. There has also been proposed a new mass transfer parameter-true water loss, which includes actual solid gain during the process. Additional consideration of a new ratio (Cichowska et al. Ratio) can be useful for better interpretation of osmotic dehydration (OD) in terms of practical applications. Apples v. Elise were dipped into 30% concentrated solutions of erythritol, xylitol, maltitol, and dihydroxyacetone (DHA) to remove some water from the tissue. To evaluate the efficiency of these solutes, 50% concentrated sucrose solution was used as a control. All of the tested osmotic agent, except maltitol, were effective in the process as evidenced by high values in the true water loss parameter. Solutions of erythritol and xylitol in 30% concentrate could be an alternative to sucrose in the process of osmotic dehydration. Peleg's, Kelvin⁻Voigt, and Burgers models could fit well with the experimental data. modeling of mass transfer parameters, using Peleg's model can be satisfactorily supplemented by Kelvin⁻Voigt and Burgers model for better prediction of OD within the particular periods of the process.

Study on the Use of Microbial Cellulose as a Biocarrier for 1,3-Dihydroxy-2-Propanone and Its Potential Application in Industry

Can microbial cellulose (MC) be used as a bio-carrier for 1,3-dihydroxy-2-propanone (DHA)? The aim of this study was to examine the possibility of using MC as a biomaterial for DHA transferring into the stratum corneum and inducing changes in skin color. The MC patches were obtained from Gluconacetobacter xylinus strain and incubated in solutions with various concentrations of DHA (g·L⁻¹: 20; 50; 80; 110) at 22 °C for 24 h. Afterwards; the patches were applied onto the skin for 15, 30, or 60 min. Skin color changes were assessed visually compared to a control patches without DHA. The intensity of skin color was increasing with the increase of DHA concentration and time of patches application. Application of MC patches with DHA (50 g·L⁻¹) for 30 min ensured the color which was considered the closest to the desired natural tan effect. MC patches containing DHA can be biocarriers enabling DHA transport into the stratum corneum and causing skin color changes. Study results indicate a new possibility for industrial applications of MC; e.g., as a biocarrier in masking the symptoms of vitiligo or production of self-tanning agents in the form of masks.

Exopolysaccharides from yeast: insight into optimal conditions for biosynthesis, chemical composition and functional properties - review

BACKGROUND

xopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates for.

METHODS

t exopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates formin.

RESULTS

t exopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates forming EPS.

Evaluation of the efficiency of different disruption methods on yeast cell wall preparation for β-glucan isolation

Selected methods for yeast cell disruption were evaluated to establish their suitability for cell wall preparation in the process of β-glucan isolation. The effect of different disruption methods on contents of total saccharides, β-glucans and proteins in the produced cell walls preparations was analyzed. The degree of cell wall purification from intracellular components was established on the basis of the ratio of solubilised material. The investigated methods included: cell exposure to hot water (autoclaving), thermally-induced autolysis, homogenization in a bead mill, sonication and their combinations. Experimental systems were prepared in water (pH 5.0 and pH 7.0) and Tris-HCl buffer (pH 8.0). The Saccharomyces cerevisiae yeast cell wall preparations with the highest degree of cytosol component release and purification of β-glucans were produced by 30 min of cell homogenization with zirconium-glass beads (0.5 mm in diameter). This was confirmed by the highest ratio of solubilised material (approx. 64%–67%). The thus-produced preparations contained ca. 60% of total saccharides, 13%–14% of β(1,3)/(1,6)-glucans, and approx. 35% of crude proteins. Similar results were obtained after autolysis coupled with bead milling as well as with sonication, but the time required for these processes was more than 24 h. Homogenization in a bead mill could be valuable for general isolation procedures because allows one to eliminate the different autolytic activity of various yeast strains.

Application of immobilized cell preparation obtained from biomass of Gluconacetobacter xylinus bacteria in biotransformation of glycerol to dihydroxyacetone

INTRODUCTION

Dihydroxyacetone (DHA), being a product of glycerol oxidation by acetic acid bacteria, is an important compound widely applied in the cosmetic, food, and pharmaceutical industry, as well as in medicine. Biotransformation of glycerol to DHA is catalyzed by glycerol dehydrogenase (GlyDH, EC 1.1.1.6) bound with the cytoplasmic membrane of bacteria. An attempt was undertaken in this study to conduct glycerol biotransformation with immobilized fractions of a cell preparation with GlyDH activity. The content of dihydroxyacetone obtained with the cell preparation was compared with its content achieved in the reaction with immobilized viable cells of G. xylinus.

MATERIAL AND METHODS

Cell walls of Gluconacetobacter xylinus bacteria were disintegrated enzymatically. The resultant preparation was immobilized on calcium alginate or first separated into two fractions (precipitate and supernatant) by centrifugation and then immobilized. DHA content was determined colorimetrically after the reaction with 3,5-dinitrosalicilic acid. Glycerol content was assayed with the refractometric method.

RESULTS

After 20 days of the process, the concentration of DHA obtained with immobilized whole cells reached 25 g/l. In turn, the content of DHA obtained in the same period with immobilized fractions of the cell preparation accounted for 16.9 g/l and 8.95 g/l (depending on the fraction applied).

CONCLUSIONS

DHA may be obtained in the process independent of G. xylinus metabolic activity using a preparation which displays the catalytic activity of glycerol dehydrogenase and obtained as a result of disintegration of live bacterial cells. The application of such a preparation may in the future eliminate technological problems posed by the presence of bacterial cells and their metabolites in the culture medium.