Psychrophilic Bacteria Research Articles

Colorimetric sensor array for the rapid distinction and detection of various antibiotic-resistant psychrophilic bacteria in raw milk based-on machine learning

In this study, a rapid, inexpensive, and accurate colorimetric sensor for detecting psychrophilic bacteria was designed, comprising gold (Au) nanoparticles (NPs) modified by d-amino acid (D-AA) as color-metric probes. Based on the aggregation of Au NPs induced by psychrophilic bacteria, a noticeable color shift occurred within 6 h. Depending on the various metabolic behaviors of bacteria to different D-AA, four primary psychrophilic bacteria in raw milk were successfully distinguished by learning the response patterns. Furthermore, the quantification of single bacteria and the practical application in milk samples could be realized. Notably, a rapid colorimetric method was constructed by combining Au/D-AA with antibiotics for the minimum inhibitory concentration of psychrophilic bacteria, which relied on differences in bacteria metabolic activity in response to diverse antibiotic treatments. Therefore, the method enables the rapid detection and susceptibility evaluation of psychrophilic bacteria, promoting clinical practicability and antibiotic management.

Production of fresh cheese analogues; the impact of soy protein isolate and oat germ powder

AbstractPlant-based proteins are being rapidly explored in the food industry to produce healthy and nutritious foods. Herein, the effects of soy protein isolate (SPI) ratio to oat germ powder (OGP) (0:0, 3.7: 6.3, 5:5, 0:10, 10:0, and 6.3:3.7%) were studied on the physicochemical, colour, rheological, microbial, antioxidant, and sensory properties of wheyless cheese. The results showed that by increasing SPI and OGP levels, ash, white index value, elastic modulus, and complex viscosity decreased, while pH, fat in dry matter, Chroma, and total colour (ΔE) increased. Also, syneresis was only observed in the control sample and was not observed in other samples. Control sample together with sample containing 10% of OGP showed the highest microbial count (i.e., mesophilic bacteria and yeasts-moulds), while samples containing 10% of SPI showed the lowest microbial count. Furthermore, the growth of both coliform and psychrophilic bacteria in all samples was negligible. Based on the results of sensory evaluation, with increasing SPI and OGP, the sensory evaluation score of samples decreased but they were within the acceptable range. According to the results obtained in this study, the combinations of 5% SPI and 5% OGP or 3.7% SPI and 6.3% OGP are recommended to be used in wheyless cheese production.

Microbial diversity in camel milk from Xinjiang, China as revealed by metataxonomic analysis.

The quality of raw camel milk is affected by its bacterial composition and diversity. However, few studies have investigated the bacterial composition and diversity of raw camel milk. In this study, we obtained 20 samples of camel milk during spring and summer in Urumqi and Hami, Xinjiang, China. Single-molecule real-time sequencing technology was used to analyze the bacterial community composition. The results revealed that there were significant seasonal differences in the bacterial composition and diversity of camel milk. Overall, Epilithonimonas was the most abundant bacterial genus in our samples. Through the annotated genes inferred by PICRUSt2 were mapped against KEGG database. Non-parametric analysis of the bacterial community prediction function revealed a strong bacterial interdependence with metabolic pathways (81.83%). There were clear regional and seasonal differences in level 3 metabolic pathways such as fat, vitamins, and amino acids in camel milk. In addition, we identified lactic acid bacteria in camel milk with antibacterial and anti-tumor activities. Our findings revealed that camel milk from Xinjiang had serious risk of contamination by psychrophilic and pathogenic bacteria. Our research established a crucial theoretical foundation for ensuring the quality and safety of camel milk, thereby contributing significantly to the robust growth of China's camel milk industry.

Effect of cinnamaldehyde-nanoemulsion and nanostructured lipid carriers on physicochemical attributes of reduced-nitrite sausages

This study aimed to produce cinnamaldehyde (CA)-loaded nanostructured lipid carriers (NLC) and nanoemulsion (NE) to replace nitrite in sausage. The NLC and NE droplet sizes were 132 and 116 nm with encapsulation efficiency of 98 and 96 %, respectively. In in vitro antimicrobial assessment, the free CA and NE showed higher microbial activity against S. aureus and E. coli than NLC. Meanwhile, NE showed a faster release profile for CA than NLC. Among the samples, NE and NE + nitrite indicated the lowest peroxide value (3.7 ± 0.1), TVBN amount (8.6 ± 0.2), acidity (0.3 ± 0.02), microbial quality (against E. coli, C. perfringens, lactic acid bacteria, psychrophilic bacteria, total mold and yeast, and total viable counts), and sensory attribute, while the NE + nitrite sample exhibited better color properties and higher oxymyoglobin content (5–10 % higher). Therefore, NE + nitrite can be the best choice due to supporting the different quality parameters of sausage.

Differential analysis of transcriptome of psychrophilic bacteria under different culture temperatures.

Psychrophilic bacteria can survive in a unique living environment. To explore the mechanism of low temperature adaptation and the physiological function of thermophilic metabolic genes. Serratia marcescens strain F13 stored in microbial laboratory was cultured at 5∘C, 10∘C and 25∘C respectively, and the obtained strains were sequenced by high-throughput transcriptome. Serratia marcescens strain CAV1761 was used as the reference strain. The data produced by transcriptome sequencing were statistically analyzed by biostatistics software such as soapnuke, soap and edger. The differentially expressed genes were found based on the gene expression, and analyzed by Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The results showed that there were 718 differential genes in F13-10 vs F13-5 comparison group, 1614 differential genes in F13-25 vs F13-5 comparison group and 1636 differential genes in F13-25 vs F13-10 comparison group. GO function enrichment analysis showed that the GO term mainly enriched by different genes in the three comparison groups was mostly related to the migration and transport of cellular or subcellular components, cell localization and transmembrane transporter activity, as well as cilia or flagella dependent cell movement. In the enrichment analysis of KEGG pathway, the three comparison groups all enriched the largest number of differential genes in the branch pathway of KEGG metabolism, followed by the branch pathway of environmental information processing. In F13-10 vs F13-5, the differential genes were mainly concentrated in 20 pathways such as ATP-binding cassette transport (ABC) transporters, thiamine metabolism and flagella assembly; In F13-25 vs F13-5, the differential genes are mainly concentrated in 20 pathways, such as (ABC) transporters, arginine and proline metabolism, two-component system and so on; In F13-25 vs F13-10, the differential genes are mainly concentrated in 20 pathways such as various types of glycan synthesis, two-component system and arginine metabolism.

Characterization of selected phages for biocontrol of food-spoilage pseudomonads.

Pseudomonas spp., such as P. fluorescens group, P. fragi, and P. putida, are the major psychrophilic spoilage bacteria in the food industry. Bacteriophages (phages) are a promising tool for controlling food-spoilage and food-poisoning bacteria; however, there are few reports on phages effective on food-spoilage bacteria such as Pseudomonas spp. In this study, 12 Pseudomonas phages were isolated from chicken and soil samples. Based on the host range and lytic activity at 30°C and 4°C and various combinations of phages, phages vB_PflP-PCS4 and vB_PflP-PCW2 were selected to prepare phage cocktails to control Pseudomonas spp. The phage cocktail consisting of vB_PflP-PCS4 and vB_PflP-PCW2 showed the strongest lytic activity and retarded regrowth of P. fluorescens and P. putida at 30°C, 8°C, and 4°C at a multiplicity of infection of 100. Nucleotide sequence analysis of the genomic DNA indicated that vB_PflP-PCS4 and vB_PflP-PCW2 phages were lytic phages of the Podoviridae family and lacked tRNA, toxin, or virulence genes. A novel endolysin gene was found in the genomic DNA of phage vB_PflP-PCS4. The results of this study suggest that the phage cocktail consisting of vB_PflP-PCS4 and vB_PflP-PCW2 is a promising tool for the biocontrol of psychrophilic food-spoilage pseudomonads during cold storage and distribution.

Structure characterization and cryoprotective activity of an exopolysaccharide from Pseudoalteromonas sp. LP6-12-2

Non-toxic natural antifreeze agents are urgently needed in many fields. Exopolysaccharides produced by psychrophilic bacteria from harsh habitats, such as Antarctica, to battle cold environments are a significant source of biological antifreeze agents. In this study, a homogeneous exopolysaccharide (EPS0-1) was extracted from Antarctica Pseudoalteromonas sp. LP6-12-2. Using High-performance gel permeation chromatography and High-efficiency anion chromatogram, respectively, the homogeneity, molecular weight, and monosaccharide composition of EPS0-1 were examined. EPS0-1 with a molecular weight (Mw) of 4351.31 kDa was an α-configuration polysaccharide containing uronic acid, amino and sulfuric acid groups, and composed of galactosamine hydrochloride, rhamnose, glucosamine hydrochloride, galactose, glucose, mannose, galacturonic acid, and glucuronic acid with rates of 1.40:9.40:4.90:32.0:37.2:6.50:4.10:4.40, respectively. Congo red test and I2-KI reaction found that the triple helix structure of EPS0-1 polysaccharide chain was weakly bound internally, with a longer side chain and/or more branches. The smooth and dense surface of EPS0-1 under Atomic force microscopy and Scanning electron microscopy revealed that it was large polysaccharide particles. Freeze-thaw cycle and freezing point determination experiment showed that EPS0-1 may significantly increase E. Coli's freezing resistance and decrease the solution's freezing point, respectively. EPS0-1 was capable of increasing the viscosity of the solution and displaying a high degree of thermal stability, which was proved by the rheological properties. And it was not hazardous to human normal liver cell line (LO2) in a specific concentration range. Therefore, the findings of this investigation established the basis for EPS0-1 as a potential antifreeze and food functional component.

A comparative study between the performance of thymol-nanoemulsion and thymol-loaded nanostructured lipid carriers on the textural, microbial, and sensory characteristics of sausage

The objective of this research was to compare the function of thymol-loaded nanostructured lipid carriers (NLC) and a thymol-nanoemulsion (NE) with nitrite (120 mg/kg) on quality parameters of sausage. The droplet size of the NLC and NE was 140 and 86.39 nm with encapsulation efficiency of 97 and 94%, respectively. The results on sausage showed that all samples containing NLC and NE exhibited the lowest increase in peroxide value, total volatile base-nitrogen, and TBA with the highest inhibitory effect on the growth of E. coli, C. perfringens, lactic acid bacteria, psychrophilic bacteria, mold and yeast, and total viable counts as well as good texture and sensory attributes with the best results in the NLC + nitrite and NE + nitrite samples. The L* and a* values were relatively higher in the samples treated with nitrite, NLC + nitrite, and NE + nitrite after 4-week storage. This increase in redness was associated with the maintenance of oxymyoglobin levels and a decrease in metmyoglobin production. The results of this study indicated that the combined use of NLC/NE (particularly NE) with 60 mg/kg nitrite significantly improved the oxidative and color stability, and delayed the spoilage and off-flavor in sausage.

Düşük Basınç Uygulaması Taze ve Depolanmış Sudak Balığının (Sander lucioperca) Fizikokimyasal ve Mikrobiyolojik Özelliklerini Geliştirdi

IIn this study, low-pressure treatment was applied to pike-perch and the changes in quality criteria during the storage process were examined. L*, a*, and b* values in samples treated with low pressure were significantly different compared to the control. It was observed that the process had an improving effect on the textural properties of the fish. While the aw value decreased to 0.822, the pH value decreased to 6.47. While TBARS values of the samples ranged between 0.014 and 0.031 mg MA / kg, TVB-N values ranged between 7.69 and 24.06 mg / 100 g. Total aerobic mesophilic bacteria, yeast/mold, total coliform group bacteria, and total aerobic psychrophilic bacteria counts of all samples exposed to low-pressure treatment were lower than the control during storage. As a result, the treatment positively affected the quality of pikeperch meat during the storage period.

Beaver-related restoration: An opportunity for sandy lowland streams in a human-dominated landscape

The expansion of beavers into human-dominated landscapes can help improve the ecological status of degraded streams. This study aimed to assess the changes in the ecological status of a degraded sandy-bottom stream under the influence of processes generated by the activity of a European beaver. We assumed that the processes in the beaver dam-and-pond complex significantly improved the physical, chemical, and bacteriological properties of water and improved the ecological status of a small lowland stream in a human-dominated landscape. To achieve these objectives, water for quality assessment, benthic invertebrates, and fish samples were collected, and the forms of land use and the natural values of the stream were analysed. In the upstream zone of the sandy-bottom stream flowing in a human-dominated landscape, the inflow of pollutants caused a significant reduction in water quality. The amount of nutrients was high and the amount of dissolved oxygen was low. Similarly, the number of meso- and psychrophilic bacteria was significantly higher than in the reference stream. The building activity of beavers initiated a series of positive environmental changes, and beaver ponds improved the self-purification of water in a polluted stream. In the lower part of the studied stream, after the stream passed through the beaver wetland system, the water quality improved, which was indicated by a significant improvement in physicochemical, microbiological, and biotic indicators, that is based on macrozoobenthos and fish. By constructing dams, beavers flooded large areas and created habitats for plant and animal species associated with wetlands, including amphibians, birds, and mammals. The improvement of the ecological status of the stream, combined with the preservation and restoration of wetland habitats in the catchment area, enables the use of ecosystem services provided by the streams in the human-dominated landscape and their surroundings.

A Mini Review on Technique of Milk Thermization

Thermization is a preheating procedure in which milk is heated at low temperatures for a brief time prior to further processing. It is often used in the dairy processing industry to make a variety of products, including pasteurized milk, milk powder, and cheese. Eliminating psychrophilic bacteria, avoiding milk spoiling, and halting the changes generated by lipase and protease enzymes are the objectives of this method. Despite the fact that thermization enhances the shelf life of milk, it may also result in sensory changes and the germination of B. cereus spores. The goal of the thermization method is to prepare milk for the upcoming processing stage, and the temperature and length of the process might vary. Thermization does not affect the flavor of milk or dairy products such as yogurt, but it may enhance the quality of cheese by decreasing the occurrence of stale and rancid flavors. The process may be carried out in a plate heat exchanger or as a pre-pasteurization treatment for raw milk to protect milk quality during lengthy storage in insulated silos.

Possibility of Prolonging Chicken Meat Shelf Life by Coating with Protein Concentrate of Quinoa Seeds

The research encompassed the production of protein casings derived from concentrated quinoa seed protein at varying concentrations (2%, 4%, 6%, 8%). The objective was to investigate the mechanical characteristics of the produced casings and their potential application in packaging refrigerated chicken breast pieces at a temperature of 4°C, with the aim of extending the storage duration for different time intervals (10, 5, 15 days). The findings pertaining to the mechanical properties of the protein casings being investigated revealed that the thickness of the membrane, tensile strength, elongation, and solubility exhibited an upward trend as the concentration increased. The findings of the microbial analysis also indicated that the application of protein casings derived from quinoa seed protein concentrate, at concentrations of 6% and 8%, on chicken breast pieces and subsequent refrigeration at 4°C, resulted in a significant reduction in the total bacterial count and the count of psychrophilic bacteria, in comparison to the control treatment where chicken pieces were left uncoated. In addition, it was observed that chicken breast portions that were coated with protein coatings exhibited no growth of coliform bacteria during the storage period, in contrast to the uncoated counterparts. The emergence of the phenomenon was observed on the tenth day of the storage period. The application of protein films on chicken breast parts resulted in a notable reduction in both the peroxide number (PV) and the value of thiarebiobutyric acid (TBA) as compared to the uncoated control treatment. The control treatment exhibited the highest values on the 15th day of refrigerated storage.

Occupational Exposure to Biological Agents in a Typical Restaurant Setting: Is a Photocatalytic Air Purifier Helpful?

According to many national legislations, biological agents represent an occupational hazard that must be managed in order to ensure safety at workplace. Bioaerosols have been associated to many pathological conditions but, despite many efforts, precise threshold limit values (TLV) are still undefined. We planned and conducted an environmental study concerning a typical restaurant that aimed to evaluate: (1) the occupational exposure to bacterial and fungal bioaerosol; (2) the efficacy of a photocatalytic air purifier device in mitigating such exposure. This observational study evaluated two dining rooms (Area 1 and Area 2) of a restaurant which can be considered typical during two consecutive weeks. Based on a national protocol, we monitored total bacterial and mycotic loads searching for two typologies of bacteria, psychrophilic bacteria (environmental contamination) along with mesophilic bacteria (human or animal origin source), and two types of fungi, mold and yeast. Baseline total bacterial load was 346.8 CFU/m3 for Area 1 and 412.9 CFU/m3 for Area 2. When the sanitizing device was operative, the total bacterial load decreased to 202.7 CFU/m3 (−41.50%—p value: <0.01) for Area 1 and to 342.2 CFU/m3 (−17.10%—p value: 0.06) for Area 2. Considering the fungal load, the mean baseline value was 189.7 CFU/m3 for Area 1 and 141.1 CFU/m3 for Area 2. When the device was kept on, the total fungal load was 108.0 CFU/m3 (−43.10%—p value: 0.055) for Area 1 and 205.0 CFU/m3 (+45.30%—p value: 0.268) for Area 2. Our findings supported the conclusion that, concerning the occupational risk derived from biological agents, a typical restaurant should be considered relatively safe. In order to mitigate or limit any possible increase of such risk, a photocatalytic device may be helpful, but not against the pollution caused by mold or yeasts. Our research also reaffirmed the need of further research assessing the kind of relationship between diseases and exposure levels, before considering the need of setting precise threshold limit values.

.Cinnamaldehyde-enriched Pickering emulsions stabilized by modified cellulose I and II nanocrystals recycled from maple leaves for shrimp preservation

The utilization of biomass waste has attracted much interest, but such attention hasn't been paid to the abundant fallen maple leaves in Canada. Herein, we aim to obtain cellulose nanocrystals (CNCs) from maple leaves and explore their potential applications as sustainable stabilizers of Pickering emulsions for the preservation of food products with complicated structures. The results reveal that two types of CNCs were extracted from maple leaves at different alkaline conditions. Octenyl succinic anhydride was selected to modify rod-like CNCs, and the CNC-stabilized oil-in-water Pickering emulsions showed excellent stability. Cinnamaldehyde, a model antibacterial compound, was incorporated in the Pickering emulsions, which exhibited the improved storage stability and sustained antibacterial capacity towards both Gram-positive and Gram-negative bacteria. Shrimp was chosen as an example that has complicated surface structure and is hard to disinfect, and the CNC-stabilized Pickering emulsions could be easily sprayed on the surface of shrimp to inhibit the proliferation of bacteria and inactivate the psychrophilic bacteria responsible for shrimp spoilage at refrigerated condition, so as to preserve the quality of shrimp. Therefore, the current work suggests the possibility to utilize fallen maple leaves as a promising source of CNCs and the applications of CNC-stabilized Pickering emulsions in seafood preservation.

The effect of hydrostatic pressure on the activity and community composition of hydrocarbon-degrading bacteria in Arctic seawater.

Increased ship traffic in the Arctic region raises the risk of oil spills. With an average sea depth of 1,000 m, there is a growing concern over the potential release of oil sinking in the form of marine oil snow into deep Arctic waters. At increasing depth, the oil-degrading community is exposed to increasing hydrostatic pressure, which can reduce microbial activity. However, microbes thriving in polar regions may adapt to low temperature by modulation of membrane fluidity, which is also a well-known adaptation to high hydrostatic pressure. At mild hydrostatic pressures up to 8-12 MPa, we did not observe an altered microbial activity or community composition, whereas comparable studies using deep-sea or sub-Arctic microbial communities with in situ temperatures of 4-5°C showed pressure-induced effects at 10-15 MPa. Our results suggest that the psychrophilic nature of the underwater microbial communities in the Arctic may be featured by specific traits that enhance their fitness at increasing hydrostatic pressure.

Biophysical and biochemical characterization of the thioredoxin system from Colwellia psychrerythraea.

The thioredoxin system is a ubiquitous oxidoreductase system consisting of the enzyme thioredoxin reductase, the protein thioredoxin, and the cofactor nicotinamide adenine dinucleotide phosphate. The system has been comprehensively studied from many organisms, such as Escherichia coli; however, structural and functional analysis of this system from psychrophilic bacteria has not been as extensive. In this study, the thioredoxin system proteins of a psychrophilic bacterium, Colwellia psychrerythraea, were characterized using biophysical and biochemical techniques. Analysis of the complete genome sequence of the C. psychrerythraea thioredoxin system suggested the presence of a putative thioredoxin reductase and at least three thioredoxin. In this study, these identified putative thioredoxin system components were cloned, overexpressed, purified, and characterized. Our studies have indicated that the thioredoxin system proteins from E. coli were more stable than those from C. psychrerythraea. Consistent with these results, kinetic assays indicated that the thioredoxin reductase from E. coli had a higher optimal temperature than that from C. psychrerythraea.

A New Ready-to-Eat Product Based on Enzymatically Peeled 'Hernandina' Clementine Segments and Citrus Syrup.

Ready-to-eat fresh fruit have an increasing presence in international markets due to their convenience and health benefits. However, these products are highly perishable and efficient technologies to increase their shelf life are needed. In the present research, different citrus fruit species and cultivars from organic farming were assessed to obtain enzymatically peeled citrus segments. The best results in terms of segment quality were observed for 'Hernandina' clementine, which was chosen to make a new ready-to-eat product based on peeled citrus segments that were packaged in glass jars with a light syrup made of citrus juice and organic sugar cane. Different citrus juice mixtures were assayed and the most appreciated syrup, based on the sensory scores given by panellists, was that containing 50-50 (v/v) of 'Fino' lemon and 'Hernandina' clementine juices. In addition, different pasteurization treatments were assessed for their effects on conserving the safety, nutritional quality and sensory properties of the product during cold storage. The results show that pasteurization treatment at 50 °C for 45 min was sufficient to prevent microbial contamination with mesophilic and psychrophilic aerobic bacteria or yeast and mould and to maintain sensory properties until five weeks of storage at 4 °C. In addition, only a 10% reduction in vitamin C concentrations was observed in fresh-segments or syrup until the end of the storage period, showing that a high bioactive compound content and health benefits were conserved in the new ready-to-eat product after pasteurization and prolonged cold storage.

Investigation of the Physiochemical and Microbiological Quality of Fruit Yoghurt Sold in Elazig Province

This study was conducted to determine some quality parameters of 25 fruit yoghurt samples (strawberry, forest fruit, blueberry, apricot, fig, mango, peach) sold in Elazig province. For this purpose, physicochemical (pH, acidity, fat, dry matter, starch, peroxidase, heat treatment) and microbiological [total mesophilic aerobic (TMA) bacteria, psychrotrophic bacteria, Lactobacillus-Leuconostoc-Pediococcus (LLP), lactic streptococcus, proteolytic and lipolytic microorganism, coliform, Enterobacteriaceae, Escherichia coli, Staphylococcus-Micrococcus, Staphylococcus aureus, Salmonella spp. and yeast-mold] analyzes of fruit yoghurt samples were performed. It was determined that 14 samples (8%) did not comply with the Turkish Food Codex Fermented Dairy Products Communiqué and TSE yoghurt standard regarding acidity value (% l.a.). The presence of starch in 91 (52%), peroxidase in 91 (52%) and heat treatment tests in 147 (84%) of the samples were positive. In the 161 (92%) samples coliform, Enterobacteriaceae and Staphylococcus-Micrococcus; and in the 154 (88%) of yeast and mold microorganisms were observed to be less than <1.0 log10 cfu/g of. Total psychrophilic bacteria, E. coli, Staphylococcus aureus, and Salmonella spp. have not emerged in any of these samples (<1.0 log10 cfu/g). There is only a statistical significance observed in Proteolytic bacteria between fruit yoghurt groups (P < 0.05). The lowest number (5.36 ± 0.10 log10 cfu/g) of proteolytic bacteria was observed in forest fruit; the highest (7.02 ± 0.52 log10 cfu/g) was determined in yoghurt with figs. As a result, it was concluded that the microbiological quality of the examined fruit yoghurt samples was not adequate for the hygienic conditions. It is thought that hygienic conditions were not considered during the production process and it could pose a risk to public health.

Microbial Community Profiling from Natural Whey Starter to Mozzarella among Different Artisanal Dairy Factories in Apulia Region (Italy)

Mozzarella is one of the most popular unripened Apulian cheeses. Knowledge about microbial composition and variability of artisanal mozzarella and its production chain is increasingly growing. In this study, microbial communities from natural whey starters to end products from four renowned Apulian artisanal dairy factories have been explored by means of 16S metagenomics. The chemical properties of mozzarella samples were also detected and analyzed. Lactobacillus is the core acidifying component of the used starters, while some psychrophilic or contaminants bacteria appear in site-specific products. Biodiversity was found to be quite similar between the whey and mozzarella sample pools, while a significant variability among production sites (factories) has been detected. Furthermore, mozzarella microbial diversity seems to be in positive correlation with its lactic acid content. Targeted metagenomics would then be a powerful and relatively quick technique to characterize the microbiological variability of traditional milk-based foods.

Preparation and potential antitumor activity of alginate oligosaccharides degraded by alginate lyase from Cobetia marina

It is of great significance to develop marine resources and study its potential biological activity by using alginate lyase produced by marine psychrophilic bacteria. In the previous study, a new marine psychrophilic bacterium (Cobetia marina HQZ08) was screened from the growth area of Laminaria japonica, and it was found that the strain could efficiently produce alginate-degrading enzyme (Aly30). In this paper, the ability of Aly30 to degrade alginate was optimized and the optimal degradation conditions were obtained. It was found that the main degradation product of alginate oligosaccharides was trisaccharide. In vitro cell experiments showed that the antitumor activity of low molecular weight alginate oligosaccharides was better than that of high molecular weight alginate oligosaccharides. In summary, Aly30 had the potential to produce alginate oligosaccharides with low degree of polymerization and antitumor activity, which provided a reference for the enzymatic preparation and application of alginate oligosaccharides.