Low-temperature adaptation and preservation revealed by changes in physiological-biochemical characteristics and proteome expression patterns in post-harvest Hami melon during cold storage.

MAIN CONCLUSION: The proteome and its time-dependent effects reveal the importance of stress response (including expression regulation of heat-shock proteins) and fatty acid metabolism in cold adaptation and preservation of Hami melon. To better understand the molecular mechanism of how Hami melons respond to low-temperature stress, this study investigated the relevant physiological characteristics, catalytic antibody activity, and quantitative proteomics of Hami melon (Jiashi muskmelon) during low-temperature storage. Jiashi muskmelon was stored inside two refrigerators set at 21 °C (control group) and 3 °C, respectively, for 24 days. Low-temperature storage led to a significantly reduced decay rate, weight loss rate, and loss of relative conductivity. It also maintained fruit firmness, inhibited the production rate of malondialdehyde and H2O2, and induced over-expression of antioxidant enzyme and ATPase. A total of 1064 differentially expressed proteins (DEPs) were identified during low-temperature storage. Stimulation response was the main process in response to low-temperature. To further verify the proteome data, we selected four heat-shock proteins (HSP) displaying relatively high expression levels. Real-time fluorescence PCR results confirmed that HmHSP90 I, HmHSP90 II, HmHSP70, and HmsHSP were significantly up-regulated upon low-temperature induction. These proteins may protect the Hami melon from physiological and cellular damage due to the low-temperature stress by acting alone or synergistically. Additionally, the main enrichment term of the fatty acid metabolism-related DEPs was fatty acid beta oxidation at 21 °C in contrast to fatty acid biosynthesis processes at 3 °C. It is speculated that Hami melon enhances low-temperature adaptability by slowing down the oxidative degradation of fatty acids and synthesizing new fatty acids at low temperatures. This study provides new insights into the mechanism of low-temperature adaptation and preservation in post-harvest Hami melon during cold storage.

Effects of high hydrostatic pressure on physicochemical and functional properties of walnut (Juglans regia L.) protein isolate.

BACKGROUND: Walnut (Juglans regia L.) is a good source of protein that has potential application in new product formation and fortification. The main objectives of this study were to investigate the effects of high hydrostatic pressure (HHP) treatment (300-600 MPa 20 min) on physicochemical and functional properties of walnut protein isolate (WPI) using various analytical techniques at room temperature. RESULTS: The results showed significant modification of solubility, free sulfhydryl content and surface hydrophobicity with increased levels of HHP treatment, indicating partial denaturation and aggregation of proteins. Differential scanning calorimetry and fluorescence spectrum analyses demonstrated that HHP treatment resulted in gradual unfolding of protein structure. Emulsifying activity index was significantly (P < 0.05) increased after HHP treatment at 400 MPa, but significantly decreased (P < 0.05) relative to the untreated WPI with further increase in pressure. HHP treatment at 300-600 MPa significantly decreased emulsion stability index. Additionally, HHP-treated walnut proteins showed better foaming properties and in vitro digestibility. CONCLUSION: These results suggest that HHP treatment could be applied to modify the properties of walnut proteins by appropriate of pressure levels, which will help in using walnut protein as a potential food ingredient.

Natural product procyanidin B1 as an antitumor drug for effective therapy of colon cancer.

Traditional chemotherapy drugs have definite antitumor mechanisms and good therapeutic efficacy; however, their poor water solubility, serious side effects and drug resistance limit their clinical application. To the best of our knowledge, the present study reported for the first time the in vivo and in vitro anticancer effects of procyanidin B1 (PCB1), a compound that is isolated from natural sources such as grape seeds, apples, peanut skin and cranberries. Cell Counting Kit-8 assay showed that PCB1 effectively decreased the number of viable HCT-116 cells compared with cells treated with the small molecule cytotoxic drug doxorubicin. Quantitative PCR and apoptosis analysis, Cell cycle analysis, and WB analysis) of the molecular mechanism showed that PCB1 induced cell apoptosis and cell cycle arrest in S phase by increasing expression of pro-apoptosis protein caspase-3 and BAX and decreasing expression of anti-apoptosis protein Bcl-2. The efficient antitumor activity of PCB1 was demonstrated through in vivo experiments on a xenograft mouse model, demonstrating that PCB1 significantly suppressed tumor growth. The present study suggested that PCB1 represents a novel class of plant-based compounds isolated from natural sources that can be applied as an anticancer drug.

Effect of high hydrostatic pressure on aroma volatile compounds and aroma precursors of Hami melon juice.

High hydrostatic pressure (HHP) treatment is an effective technique for processing heat-sensitive fruits and causes changes in volatile compounds and their precursors while maintaining quality. We investigated the changes and correlations of volatile compounds, related enzyme activities and precursor amino acids, and fatty acids in Hami melon juice under 350-500 MPa pressure. The application of HHP treatment resulted in a considerable reduction of esters and a substantial increase in aldehydes and alcohols in C6 and C9. Activities of lipoxygenase (LOX), alcohol acyltransferase (AAT), and phospholipase A2 (PLA2) were lower than those of the untreated group, alcohol dehydrogenase (ADH) activity was reversed. When compared to fresh cantaloupe juice, there was an increase in both the types and contents of amino acids with lower total fatty acid contents than the control group. Positive correlations were observed among six ester-related substances and eight alcohol-related substances. Additionally, the correlations between volatile compounds and fatty acids were more substantial compared to those between volatile compounds and amino acids. HHP treatment increases Hami melon flavor precursors and is an effective way to maintain the aroma volatile compounds and flavor of Hami melon juice.

Preparation and Characterization of Phenolic Acid-Chitosan Derivatives as an Edible Coating for Enhanced Preservation of Saimaiti Apricots.

In this study, caffeic acid (CA) and chlorogenic acid (CGA) were incorporated onto chitosan (CS) using free radical grafting initiated by a hydrogen peroxide/ascorbic acid (H2O2/Vc) redox system. The structural properties of the CA (CA-g-CS) and CGA (CGA-g-CS) derivatives were characterized by UV-Vis absorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and thermal stability analysis. Then, the antioxidant and antibacterial properties were evaluated, and the effect of CGA-g-CS on the postharvest quality of Saimaiti apricot was studied. It proved that phenolic acids were successfully grafted onto the CS. The grafting ratios of CA-g-CS and CGA-g-CS were 126.21 mg CAE/g and 148.94 mg CGAE/g. The antioxidation and antibacterial activities of CGA-g-CS were better than those of CA-g-CS. The MICs of CGA-g-CS against E. coli, S. aureus, and B. subtilis were 2, 1, and 2 mg/mL. The inhibitory zones of 20 mg/mL CGA-g-CS against the three bacteria were 19.16 ± 0.35, 16.33 ± 0.91, and 16.24 ± 0.05 mm. The inhibitory effects of 0.5% CGA-g-CS on the firmness, weight loss, SSC, TA, relative conductivity, and respiration rate of the apricot were superior. Our results suggest that CGA-g-CS can be potentially used as an edible coating material to preserve apricots.

Identification and characterization of volatile compounds in Lentinula edodes during vacuum freeze-drying.

In this study, modified headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) and electronic nose (E-nose) were utilized to investigate the dynamic aroma changes of Lentinula edodes (L. edodes) at different stages of vacuum freeze drying (VFD). The extraction efficiency of volatile compounds from vacuum freeze-dried L. edodes was improved by optimizing five parameters of the HS-SPME. A total of 50 volatiles were identified in L. edodes from different VFD stages by GC-MS. Alcohols, aldehydes, and volatile sulfur-containing compounds (VSCs) were the main flavor constituents of fresh L. edodes, frozen L. edodes, and secondary dried L. edodes. Aldehydes, ketones, and VSCs were the main aroma groups in L. edodes after primary drying. There were 20 volatiles as key odorants with the odor activity values greater than 1, in which esters appeared only before secondary drying of L. edodes. These findings could contribute to a comprehensive insight into the formation mechanism of flavor in the VFD process of L. edodes. PRACTICAL APPLICATIONS: Lentinula edodes is the second most widely cultivated edible fungus worldwide. It is considered a valuable health food not just because of its abundance of nutrients but also because of its delicious taste. This study investigated the regularity regarding the changes of volatile compounds in L. edodes during vacuum freeze drying. The results of the present study offer valuable knowledge for the formation mechanism of volatile substances in the drying process of L. edodes, which can be beneficial to promote the development and utilization of flavor substances in L. edodes.

Antimicrobial resistance of Escherichia coli isolated from retail foods in northern Xinjiang, China.

To determine antimicrobial resistance, 431 samples of retail foods purchased at different supermarkets in Northern Xinjiang were examined in this study. There were 112 Escherichia coli strains that were isolated, with approximately 26% of the samples contaminated by E. coli. The detection rate of E. coli isolated from pork was the highest (59.6%), followed by mutton (52.6%), retail fresh milk (52.4%), duck (36.4%), beef (35.3%), chicken (33.3%), and ready-to-eat food (12.9%); the E. coli detection rate for fish and vegetables was <11%. The result showed that the 112 isolates were mostly resistant to tetracycline (52%), followed by ampicillin (42%), compound trimethoprim/sulfamethoxazole (37%), amoxicillin (33%), and nalidixic acid (32%), imipenem resistance was not detected. One hundred isolates carried at least one antimicrobial resistance gene. The detection rate of resistance genes of our study was as follows: tetA (38%), tetB (27%), bla OXA (40%), bla TEM (20%), floR (20%), sul1 (16%), sul2 (27%), aad Ala (19%), aadB (11%), strA (28%), and strB (24%); tetC and bla PSE were not detected. Virulence genes fimC, agg, stx2, fimA, fyuA, papA, stx1, and eaeA were found in 52, 34, 21, 19, 6, 3, 2, and 2 isolates, respectively; papC was not detected. There was a statistically significant association between fimC and resistance to ciprofloxacin (p = .001), gentamicin (p = .001), amikacin (p = .001), levofloxacin (p = .001), and streptomycin (p = .001); between fimA and resistance to tetracycline (p = .001), ampicillin (p = .001), compound trimethoprim/sulfamethoxazole (p = .001), and amoxicillin (p = .003); between agg and resistance to gentamicin (p = .001), tetracycline (p = .001), ciprofloxacin (p = .017), and levofloxacin (p = .001); and between stx2 and resistance to ampicillin (p = .001), tetracycline (p = .001), compound trimethoprim/sulfamethoxazole (p = .002), and amoxicillin (p = .015).

Effect of high hydrostatic pressure on aroma components, amino acids, and fatty acids of Hami melon (Cucumis melo L. var. reticulatus naud.) juice.

The changes and relationships between the volatile compounds and fatty acids, and between volatile compounds and free amino acids were analyzed after they were handled by 400 and 500 MPa (45°C/10 min) high hydrostatic pressure (HHP). The volatile components of 31, 30, and 32 were detected in the untreated, 400, and 500 MPa samples, respectively. Unlike the ketones and acids, the three contents, including ester (59.59%-71.34%), alcohol (5.95%-7.56%), and aldehyde (0.36%-1.25%), were greatly changed. While HHP treatment exerted a few effects on the contents of 12 kinds of fatty acids. With the increase in pressure, the contents of palmitic acid, linolenic acid, and α-linolenic acid were remarkably reduced. The correlations between flavor compounds and amino acids, and between flavor compounds and fatty acids were studied by Pearson's correlation analysis and visualized with using the corrplot package in R software. The analysis showed that the amino acids were positively correlated with (E)-6-nonenal, (2E,6Z)-nona-2,6-dienal and (Z)-6-nonen-1-ol, while they were negatively correlated with nonanal, (Z)-3-hexen-1-ol and ethyl caproate. Besides, the fatty acids were positively correlated with the esters of 2,3-butanediol diacetate and 2-methyl propyl acetate, while they were negatively correlated with (E)-2-octenal and (Z)-6-nonen-1-ol.

[Determination of mineral elements in eight pear varieties by ICP-MS after microwave-assisted digestion].

A study was carried out on the contents of mineral elements such as Na, K, Ca, Mg, Zn, Cu, Fe, Mn and B in eight different pear varieties by ICP-MS after microwave-assisted digestion. The results indicated that the main elements of the eight pears are similar, but the content of each element is different. The content of K is the highest in the detected pears, followed by Mg, Ca and Na. Compared with the reference value of AIJN (Association of Industry of Juices and Nectars from fruits and vegetables of the European Union), the range scale of K, Mg, and Ca was higher than that of the AIJN, while the content of Na element was lower than that of the AIJN, and other elements content was consistent with it.

Improvement of lipid production in oleaginous yeast Rhodosporidium toruloides by ultraviolet mutagenesis.

The oleaginous yeast Rhodosporidium toruloides AS 2.1389 is viewed as desirable industrial microorganisms that can accumulate a high content of lipids for biodiesel production. In this study, we attempted to improve lipid accumulation in the yeast Rhodosporidium toruloides by UV irradiation mutagenesis and selection based on lithium chloride tolerance or ethanol-H2O2 tolerance. The biomass concentration, lipid yield and glucose consumption of mutant R. toruloides were determined. The transcription levels of lipid accumulation-related genes in the wild-type and mutant strains were also determined. The lithium chloride-tolerant strain R-ZL2 and the ethanol-H2O2-resistant strain R-ZY13 were generated by UV mutagenesis. The two mutant strains showed greater lipid productivity and lipid yield compared to the wild type. Transcriptional analysis revealed that IDP1, GPD1 and GND were expressed at significantly higher levels in the two high-lipid-producing mutants. In conclusion, lipid productivity and lipid yield in R. toruloides were successfully improved via UV mutagenesis and selection. We also identified some lipid accumulation-related genes for improving lipid productivity through genetic engineering.

Microbial community composition on grape surface controlled by geographical factors of different wine regions in Xinjiang, China.

Native microorganisms on wine grape surface contribute to regional wine characteristics and quality. The Xinjiang Uygur Autonomous Region in northwest China is one of the eight main wine-producing areas in China. To investigate the relationship between the microbial community structure of wine grape epidermises and environmental conditions, 16S rDNA and ITS sequences of 48 wine grape samples from four wine grape cultivars and six wine-growing regions in Xinjiang were sequenced, based on Illumina high-throughput sequencing technology. A total of 691 operational taxonomic units (OTUs) in 16 bacterial phyla and 349 OTUs in three fungal phyla were identified. Among them, Proteobacteria and Ascomycota were the predominant bacteria and fungi, respectively. Canonical correspondence analysis indicated that bacterial community diversity was largely related to altitude, latitude and longitude, while that of the fungi was closely related to altitude, dryness, frost-free period, latitude and longitude. Our results suggest that microbial community structure on the surface of wine grape is controlled primarily by geographical conditions.

Cloning and stress-responding expression analysis of malonyl CoA-acyl carrier protein transacylase gene of Nannochloropsis gaditana.

Malonyl CoA-acyl carrier protein transacylase (MCAT, E2.3.1.39) is closely associated with the FASII pathway of fatty acid biosynthesis. However, the information about microalgal MCAT is scarce. In this study, a MCAT gene was isolated from Nannochloropsis gaditana with its deduced protein (NgMCAT) characterized with bioinformatic tools. The abundance of the NgMCAT transcript under different environmental conditions was determined with real-time quantitative PCR. Results showed that the open reading frame (ORF) of NgMCAT was 1059 bp in length, which encoded 352 amino acid residues. The abundance of NgMCAT transcript reached the maximum (5.17-fold) at 6h when sodium nitrate was limited, and reached the maximum (4.25-fold) at 12h at low temperature (15°C). The abundance of NgMCAT transcript fluctuated at high temperature (35°C) when the concentration of nitrate and sodium chloride exceeded 150 mg/L and 62 g/L, respectively. In addition, some components of fatty acid that changed with the expression of NgMCAT were also observed.

Transcriptome sequencing, annotation and expression analysis of Nannochloropsis sp. at different growth phases.

Nannochloropsis sp. is an oil-rich microalga. The lipid content of cells at stationary growth phase was much higher than that of cells at logarithm growth phase, but very little information focusing on the abundances of gene transcripts concerning lipid accumulation is available. In present study, the second generation Illumina sequencing was used to investigate the genes and pathways of Nannochloropsis sp. in order to identify those involved in lipid metabolism. In total, 29,203 unigenes were obtained from logarithm and stationary growth phases. The transcripts of some unigenes were differentially abundant at two growth phases. Among the unigenes obtained, about 195 unigenes were involved in lipid metabolism and 315 unigenes were putatively transcription factors. These genes are a very useful resource for the future studies of Nannochloropsis sp.

Influence of thermal and dense-phase carbon dioxide pasteurization on physicochemical properties and flavor compounds in Hami melon juice.

The influence of thermal and dense-phase carbon dioxide (DP-CO(2)) pasteurization on physicochemical properties and flavor compounds in Hami melon juice was investigated. Melon juice was pasteurized using DP-CO(2) treatment and compared to a conventional high-temperature-short-time (HTST) method. The DP-CO(2) treatment was carried out using a DP-CO(2) unit (55 degrees C, 60 min, and 35 MPa). The thermal pasteurization was performed at 90 degrees C for 60 s with an adapted laboratory setup. Effects of variations to both treatments on pH and concentrations of microbes, beta-carotene, ascorbic acid, sugars, organic acids, and volatile compounds were investigated. The changes of pH and organic acid and sugar concentrations were not significant. There were significant differences between treatments in microbial count, vitamin C, beta-carotene, and volatile compound concentrations. In general, DP-CO(2) treatment had less of an effect on the measured variables than the thermal treatment.