Enhancing viability of dried lactic acid bacteria prepared by freeze drying and spray drying via heat preadaptation.

Physical injury carried by dried process was an inevitable and hostile problem which could seriously affect the quality and viability of microbial agents. In this study, heat preadaptation was successfully applied as a pretreatment to fight against the physical stresses encountered during freeze-dried and spray-dried process and develop a high activity Tetragenococcus halophilus powder. The results indicated T. halophilus cells maintained a higher viability in dried powder when cells were treated with heat preadaptation before dried process. Flow cytometry analysis illustrated that heat preadaptation contributed to maintain a high membrane integrity during dried process. Besides, glass transition temperatures of dried powder increased when cells were preheated, which further verified that higher stability was obtained in group preadaptation during shelf life. Additionally, dried powder prepared by heat shock presented a better fermentation performance, suggesting heat preadaptation may be a promising strategy to prepare bacterial powder by freeze drying or spray drying.

Profiling the composition and metabolic functions of microbial community in pellicle-forming radish paocai.

Pellicle formation is an obvious indicator of spoilage and is followed by a loss of flavor in a variety of fermented vegetables. In this study, the pellicle-forming microorganisms were isolated using culture-dependent approaches, then a comparative analysis between the pellicle-forming (PF) radish paocai and normal fermented paocai in the diversity and function of microbial community was conducted by metagenome sequencing. Based on a pairwise t-test and OPLS-DA analysis, diallyl sulfide, (z)-1-allyl-2-(prop-1-en-1-yl) disulfane, and terpineol were considered to be the main components responsible for the unpleasant flavor of PF paocai. Yarrowia spp., Enterobacter spp., and Pichia spp. were the main pellicle-forming microorganisms. All 17 isolated Enterobacter strains showed pectinase-producing and cellulase-producing abilities, and 3 isolated Pichia strains showed gas-producing capacity. According to LEfSe analysis based on metagenomes, unclassified_g__Citrobacter and Yarrowia lipolytica were the uppermost biomarkers that distinguished the PF paocai from normal paocai. Unclassified_g__Lactobacillus and Lactobacillus plantarum were found to be actively engaged in starch and sucrose metabolism, cysteine and methionine metabolism, galactose metabolism, fructose and mannose metabolism, lysine biosynthesis, fatty acid biosynthesis, and arginine biosynthesis, all of which contributed to the flavor formation of paocai. Combining the results of metagenome sequencing with the data obtained based on the culture-dependent method, we could deduce that the growth of Yarrowia lipolytica first promoted the increase of pH and the formation of pellicle, which provided a suitable niche for the growth of some harmful bacteria such as Enterobacter, Citrobacter, and Serratia. These hazardous bacteria then worked in concert to induce the odorous stench and texture softening of paocai, as well as more pellicle formation.

Effects of salt concentration on the quality and microbial diversity of spontaneously fermented radish paocai.

Paocai is a traditional Chinese fermented vegetable product popular in Asian countries. As an important additive, salt concentration is closely related to the quality of paocai. The aim of this study was to investigate the effect of salt concentration on the physicochemical characteristics, microbial diversity, and flavor profiles of spontaneously fermented radish, and the cross-correlation between microorganisms and flavor compounds was also revealed. Analysis of the microbial diversity of paocai showed that Firmicutes, Proteobacteria, and Ascomycota were detected as the main phyla with different salt concentrations, Weissella and Lactobacillus were the predominant bacterial genera, and Yarrowia dominated the fungal genera. Based on LEfSe analysis, Lactobacillus, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Microbacterium, Lactococcus, Staphylococcus, and Weissella were regarded as differential genera caused by differences in salinity. Analysis of the flavor compounds showed that 17 free amino acids, 5 isothiocyanates, 3 terpenes, 15 sulphur-containing compounds, 16 esters, 8 organic acids, 9 aldehydes, 8 ketones, 25 alcohols, 7 nitriles, 2 lactones, and 10 hydrocarbons were detected. Then, the correlation between the microbial community and flavor compounds was revealed, and the results indicated that several bacterial genera significantly correlated with flavors, including Lactobacillus, Kosakonia, Weissella, Leuconostoc, and Staphylococcus, while fungi had weak correlations with flavors. In addition, Metacyc pathway analysis was carried out to elucidate the effect of salt content on the metabolic pathways, showing that most flavor-related pathways were up-regulated with the increase in salt content. Results presented in this study may contribute to further understanding the role of salt in the fermentation of paocai and provide effective references for quality control of traditional fermented vegetables.

A novel exopolysaccharide produced by Zygosaccharomyces rouxii with cryoprotective and freeze-drying protective activities.

In the present work, a novel exopolysaccharide EPS-3791 was extracted and purified from a salt-tolerant yeast, Zygosaccharomyces rouxii. Structural analyses showed that EPS-3791 was composed of galactose, glucose and mannose in a molar ration of 1.00: 4.25: 13.30 with a molecular weight of 64.412 kDa. Fourier transform infrared spectroscopy manifested the main functional groups, α- and ß- configurations. Methylated analysis indicated T-Manp-(1→, →2)-Glcp-(1 â†’ and â†’ 2,6)-Manp-(1 â†’ were the main linkages. 800 MHz nuclear magnetic resonance spectroscopy demonstrated the EPS-3791 structure of a novel main chain and branched chain. Atomic force microscope and scanning electron microscope revealed a homogeneous and uniform porous structure. In addition, EPS-3791 was proven to have cryoprotective and freeze-drying protective effects on Lactococcus lactis, and exhibited better protective performance than that of trelahose during freeze-drying of L. lactis, suggesting that EPS-3791 could be developed into cryoprotectant or lyoprotectant applied in food industry.

MAEA rs6815464 polymorphism and periodontitis in postmenopausal Japanese females: A cross-sectional study.

OBJECTIVES: Macrophage erythroblast attacher (MAEA) is a membrane protein that regulates the development of mature macrophages by mediating attachment with erythroblasts. A polymorphism rs6815464 (C/G) in MAEA gene was reported to be associated with type II diabetes. Along with diabetes, osteoporosis shows an increased prevalence in postmenopausal females, and both diseases have been reported to be associated with periodontitis. Therefore, we explored the relevance of the MAEA polymorphism to periodontitis, bone mineral density (BMD) and haemoglobin A1c (HbA1c). DESIGN: This was a cross-sectional study with the final sample comprised of 344 postmenopausal Japanese females. Probing pocket depth (PPD) and clinical attachment level (CAL) were measured. Genotype was determined by TaqMan assay. Blood biochemical parameters and BMD of the lumbar spine were evaluated. RESULTS: No differences were found in age, body mass index, HbA1c, BMD, number of teeth, bone metabolism parameters between the genotypes. Mean CAL and percentage of sites with PPD or CAL ≥ 5 mm were higher in the G-allele carriers than in the non-carriers. Multiple logistic regression analyses revealed that G-allele carriage was associated with severe periodontitis (odds ratio = 3.73, 95% CI = 1.36-10.19). CONCLUSION: Our results suggested that the MAEA gene polymorphism was independently associated with severe periodontitis.

A polymorphism rs6815464 in the macrophage erythroblast attacher gene is associated with low bone mineral density in postmenopausal Japanese women.

BACKGROUND AND PURPOSES: Osteoporosis and osteopenia are multifactorial diseases characterized by low bone mineral density (BMD) and are susceptible to genetic and environmental risk factors. The macrophage erythroblast attacher (MAEA) was discovered as a protein to mediate the attachment of erythroid cells to macrophages and is essential for bone marrow hematopoiesis. MAEA is expressed in a wide range of cells and tissues including osteoblasts and osteoclasts. Recent studies have shown that a single nucleotide polymorphism (SNP) rs6815464 (C/G) in the MAEA gene increases the susceptibility of type 2 diabetes mellitus. However, the contribution of MAEA to bone metabolism remains unknown. Therefore, we performed this study to evaluate the association between MAEA polymorphism and low BMD. METHODS: In a cross-sectional study with postmenopausal Japanese women living in the Yokogoshi area, Niigata City, we evaluated whether rs6815464 was associated with low BMD. Blood samples were collected from 353 subjects (age 63.8 ±â€¯5.4 years). The MAEA genotype was determined by TaqMan assay. BMD was assessed by dual-energy X-ray absorptiometry at the lumbar spine (L2-L4), hip and femoral neck. Low BMD was defined as a T-score <-1. RESULTS: The percentage of subjects with low BMD in the lumbar spine, total hip and femoral neck were 71%, 75% and 84% respectively. After adjusting age, BMI, HbA1c, smoking and alcohol consumption, the G-allele carriage was found to be associated with low BMD of total hip (odds ratio = 2.11, 95% CI: 1.14-3.91, P = 0.018), but not of the lumbar spine or femoral neck. CONCLUSION: The MAEA gene polymorphism rs6815464 was associated with low hip BMD in postmenopausal Japanese women.

Rapid fluorescence detection of pathogenic bacteria using magnetic enrichment technique combined with magnetophoretic chromatography.

A rapid and sensitive analytical method was developed to detect pathogenic bacteria which combined magnetic enrichment, fluorescence labeling with polyethylene glycol (PEG) magnetophoretic chromatography. As pathogenic bacteria usually exist in complex matrixes at low concentration, an efficient enrichment is essential for diagnosis. In order to capture series types of pathogenic bacteria in samples, amino-modified magnetic nanoparticles (Fe3O4@SiO2-NH2) were prepared for efficient enrichment by the electrostatic interaction with pathogenic bacteria. It was shown that the capture efficiency reached up to 95.4% for Escherichia coli (E. coli). Furthermore, quantitative analysis of the bacteria was achieved by using acridine orange (AO) as a fluorescence probe for the captured E. coli due to its ability of staining series types of bacteria and rapid labeling. In order to remove the free magnetic nanoparticles and redundant fluorescent reagent, the labeled suspension was poured into a PEG separation column and was separated by applying an external magnetic field. The presence of 100 cfu mL-1 E. coli could be detected for semi-quantitative analysis by observing the separation column with the naked eye, and the concentration could be further evaluated by fluorescence detection. All the above processes were finished within 80 min. It was demonstrated that a good linear relationship existed between the fluorescence intensity and the concentration of E. coli ranging from 102 to 106 cfu mL-1, with a detection limit of 100 cfu mL-1 when E. coli acted as target bacteria. The recovery rate of E. coli was 93.6∼102.0% in tap water and cooked meat samples, and the RSD was lower than 7% (n = 6); the result coincided with the conventional plate count method. Graphical abstract ᅟ.

A type of novel fluorescent magnetic carbon quantum dots for cells imaging and detection.

A new type of multifunctional fluorescent magnetic carbon quantum dots SPIO@CQDs(n) ([superparamagnetic iron oxide nanoparticles (SPIO), carbon quantum dots, (CQDs)]) with magnetic and fluorescence properties was designed and prepared through layer-by-layer self-assembly method. The as-synthesized SPIO@CQDs(n) exhibited different emission colors including blue, green, and red when they were excited at different excitation wavelengths, and its fluorescent intensity increased as the increase of CQD layer (n). SPIO@CQDs(n) with quite low toxicity could mark cytoplasm with fluorescence by means of nonimmune markers. The mixture sample of liver cells L02 and hepatoma carcinoma cells HepG2 was taken as an example, and HepG2 cells were successfully separated and detected effectively by SPIO@CQDs(n), with a separation rate of 90.31%. Importantly, the designed and prepared SPIO@CQDs( n ) are certified to be wonderful biological imaging and magnetic separation regents.