A Biomass-Based Colorimetric Sulfur Dioxide Gas Sensor for Smart Packaging.

Sulfur dioxide (SO2) gas, which can effectively prohibit the growth of pathogenic microorganisms, has been internationally used in commercial food packaging to maintain high-quality food and reduce the incidence of foodborne illnesses. However, the current mainstream methods for SO2 detection are either large and expensive instruments or synthesized chemical-based labels, which are not suitable for large-scale gas detection in food packaging. Recently, we discovered that petunia dye (PD), which is extracted from natural petunia flowers, demonstrates a highly sensitive colorimetric response to SO2 gas with its total color difference (ΔE) modulation reaching up to 74.8 and detection limit down to 1.52 ppm. To apply the extracted petunia dye in smart packaging for real-time gas sensing and food-quality prediction, a flexible and freestanding PD-based SO2 detection label is prepared by incorporating PD in biopolymers and assembling the films through a layer-by-layer approach. The developed label is utilized to predict grapes' quality and safety by monitoring the embedded SO2 gas concentration. The developed colorimetric SO2 detection label could potentially be used as an intelligent gas sensor for food status prediction in daily life, food storage, and supply chains.

Preparation and insecticidal performance of sustained-release cinnamon essential oil microemulsion.

BACKGROUND: To improve the utilization rate of cinnamon essential oil and compensate for the shortcomings of its easy decomposition and oxidation, the microemulsion of cinnamon essential oil was prepared using Tween 80 and anhydrous ethanol as surfactant and cosurfactant, respectively. The effects of the surfactant type, Km value, preparation temperature and aqueous pH on the quality of the microemulsion were studied via a pseudo-ternary phase diagram. The slow-release performance of cinnamon essential oil microemulsion and the control performance of the insect repellent package on the rice weevil were characterized. RESULTS: The results showed that, when Tween 80 was used as a surfactant and anhydrous ethanol was used as a cosurfactant, the Km value was 3:1, preparation temperature was 40 °C, aqueous pH was 5 and prepared cinnamon essential oil microemulsion was of the O/W type. The microemulsion had strong stability and a 81.5-nm concentrated particle size distribution, and possessed excellent embedding and sustained-release effects. The prepared insect repellent active package prolongs the use time and the effect of cinnamon essential oil. The repellent rate of the rice weevil was as high as 100% after 48 h, and the contact mortality and fumigation mortality rates of the rice weevil also reached 96.67% and 86.67%, respectively, after 96 h. CONCLUSION: The prepared cinnamon essential oil microemulsion and active packaging had a good sustained-release effect. © 2021 Society of Chemical Industry.

Effect of citronella essential oil fumigation on sprout suppression and quality of potato tubers during storage.

Effect of citronella essential oil (CEO) fumigation on sprout suppression and quality of potato tubers during storage was investigated. Potato tubers were treated under conditions of single-phase (30 µL L-1, 0-10 d) and dual-phase (30 µL L-1, 0-10 d; 30 µL L-1, 35-90 d) fumigation. Changes in germination rate, weight loss, starch, reducing sugar, gibberellins (GA3), and α-solanine were measured. The results showed that CEO fumigation could control sprouting and improve the quality of potato tubers during storage compared to the non-treated tubers. CEO treatments inhibited the degradation of starch and the increase of reducing sugar content. The production of gibberellins (GA3) was suppressed, and the levels of α-solanine in the skin and flesh of potato tubers were decreased by CEO fumigation. Dual-phase CEO fumigation had a better effect on sprout suppression than single-phase fumigation, and possesses potential for postharvest application.

Application of a Predictive Growth Model of Pseudomonas spp. for Estimating Shelf Life of Fresh Agaricus bisporus.

For prediction of the shelf life of the mushroom Agaricus bisporus, the growth curve of the main spoilage microorganisms was studied under isothermal conditions at 2 to 22°C with a modified Gompertz model. The effect of temperature on the growth parameters for the main spoilage microorganisms was quantified and modeled using the square root model. Pseudomonas spp. were the main microorganisms causing A. bisporus decay, and the modified Gompertz model was useful for modelling the growth curve of Pseudomonas spp. All the bias factors values of the model were close to 1. By combining the modified Gompertz model with the square root model, a prediction model to estimate the shelf life of A. bisporus as a function of storage temperature was developed. The model was validated for A. bisporus stored at 6, 12, and 18°C, and adequate agreement was found between the experimental and predicted data.

Effects of UV-C treatment and cold storage on ergosterol and vitamin D2 contents in different parts of white and brown mushroom (Agaricus bisporus).

Effects of ultraviolet-C (UV-C) treatment (0.5, 1.0 and 2.0kJ/m(2)) and cold storage on ergosterol and vitamin D2 content in different parts of white and brown button mushrooms (Agaricus bisporus) were investigated. UV-C treatment did not significantly affect ergosterol content in the caps and stems of the two mushrooms, but ergosterol content increased significantly during 14days cold storage. Vitamin D2 content in the caps and stems of two mushrooms significantly increased as UV-C dose increased, and 2.0kJ/m(2) UV-C showed the best result. During cold storage, vitamin D2 content in the caps of the two mushrooms decreased from day 1 to day 7, and then kept stable until day 14, but vitamin D2 content in the stems of brown mushrooms kept increasing for the whole 14days period. UV-C could increase vitamin D2 contents in both caps and stems of white and brown mushrooms without significantly affecting ergosterol content.

[Effects of Red Light-Emitting Diode (LED) on the Postharvest Yellowing Change of Broccoli].

As an important factor affecting the growth and development of plants, light gives wide range regulating effects on physiological metabolisms, photosynthesis characteristic, quality and aging of plants during the growth . However, the research whether light can improve the quality of fruits and vegetables and prolong the storage period of is rarely reported home and abroad. Three monochromatic light , red, blue and green were used to the irradiation of broccoli. It was found that the inhibitory effect of red light could inhibit yellowing of postharvest broccoli better than that of blue light while green light could accelerate the yellowing, therefore this paper focused on the yellowing inhibitory effect of LED monochromatic red light on postharvest broccoli. The LED monochromatic red light with wavelength (625±5)nm, light intensity (100±5)Lx was used to provide continuous irradiation to broccoli with no light treatment as control. The results showed that: LED monochromatic light could inhibit the increase of chromatic aberration L value. The chromatic aberration -a/b value was maintained and the chlorophyll degradation was delayed. Meanwhile, the broccoli commodity was effectively maintained because of the delay of the respiration peak and the reduction of respiratory intensity as well as ethylene release rate . Correlation analysis showed that, after red LED monochromatic light treatment of broccoli, a positive very significant correlation (p<0.01) was found between the ethylene release rate and yellowing index. Compared with conventional no-light, treatments of LED monochrome red could extend the storage period around 5d for broccoli, and the results can provide a theoretical basis for cold storage of Broccoli.

Production of medium-chain volatile flavour esters in Pichia pastoris whole-cell biocatalysts with extracellular expression of Saccharomyces cerevisiae acyl-CoA:ethanol O-acyltransferase Eht1 or Eeb1.

Medium-chain volatile flavour esters are important molecules since they have extensive applications in food, fragrance, cosmetic, paint and coating industries, which determine different characteristics of aroma or taste in commercial products. Biosynthesis of these compounds by alcoholysis is catalyzed by acyl-CoA:ethanol O-acyltransferases Eht1 or Eeb1 in Saccharomyces cerevisiae. In this study, these two yeast enzymes were selected to explore their preparations as the form of whole cell biocatalysts for the production of volatile flavour esters. Here, the novel whole cell biocatalysts Pichia pastoris yeasts with functional extracellular expression of Eht1 or Eeb1 were constructed. Flavour production was established through an integrated process with coupled enzyme formation and ester biosynthesis in the recombinant yeasts in one pot, leading to the formation of volatile C6-C14 methyl and ethyl esters from wort medium. Interestingly, there is no significant difference between P. pastoris-EHT1 and P. pastoris-EEB1 in substrate preference during flavour biosynthesis, indicating a similar role of Eht1 and Eeb1 in P. pastoris cells, in contradiction with previous findings in S. cerevisiae to some extent. Consequently the study not only provides a greater understanding of these two enzymes in a heterogeneous host, but also demonstrated the positive effect of the recombinant Eht1 and Eeb1 in ester formation by P. pastoris live cells, potentially paving the way towards achieving efficient production of volatile flavour by an integrated biocatalytic system composed of recombinant enzyme production and flavour biosynthesis.

Fate of E. coli O157:H7, Salmonella spp. and potential surrogate bacteria on apricot fruit, following exposure to UV-C light.

Some soft fruit, such as tree-ripened apricots, cannot be washed with aqueous sanitizers, due to their innate softness and delicate surfaces. In this study, ultraviolet-C (UV-C) light was investigated for its efficacy in inactivating 4-5 individual strains of Escherichia coli O157:H7 and Salmonella spp. on apricots, in addition to a four-strain composite of Shiga toxin-negative E. coli O157:H7 and a cocktail of three attenuated strains of Salmonella Typhimurium and Salmonella Typhimurium LT2. Also, the survival of E. coli O157:H7 and Salmonella spp. after exposure to 74 and 442 mJ/cm² of UV-C was evaluated during post-UV storage at 2 and 20 °C. The fruit was spot inoculated and the areas (ca. 1.5 cm²) of fruit surface with the inoculated bacteria were exposed to UV-C at 7.4 mW/cm². E. coli O157:H7 and Salmonella spp. populations decreased rapidly (1-2 logs) (P<0.05) with increasing UV-C doses of 0 to 74 mJ/cm². Further increases in UV-C dosage achieved only limited additional reductions in bacterial populations. Shiga toxin-negative bacteria and attenuated S. Typhimurium strains, along with S. Typhimurium LT2, responded similarly to corresponding pathogenic E. coli O157:H7 and Salmonella spp. During storage at 2 or 20 °C, populations of pathogenic E. coli O157:H7 and Salmonella spp. on untreated fruit decreased slowly; however, populations on fruit treated with 442 mJ/cm² decreased rapidly at both temperatures. After 8 days at 20 °C or 21 days at 2 °C, E. coli O157:H7 and Salmonella spp. populations on UV-C treated fruit were at least 2 log CFU/g lower than on non-treated controls. Our results suggest that surface-inoculated bacteria survived poorly following UV-C treatment of apricots.

In vitro antifungal activity and mechanism of action of chitinase against four plant pathogenic fungi.

To determine why chitinase has different antifungal activity on different pathogenic fungi in vitro, we purified recombinant rice chitinase from Pichia pastoris and investigated its antifungal activity against four fungi - Rhizopus stolonifer (Ehrenb. et Fr.) Vuill, Botrytis squamosa Walker, Pythium aphanidermatum (eds.) Fitzp, and Aspergillus niger van Tiegh. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the surface microstructure and proportion of chitin in the cell wall of the four fungi, respectively. The results showed that the chitinase exhibited different antifungal activities against the four fungi, which was directly correlated to the surface microstructure and the proportion of chitin in the fungal cell wall. It will help understanding the antifungal mechanism of the recombinant chitinase and further determining its application scope on crop protection and post-harvest storage of fruits and vegetables.

High-level expression of fusion protein containing 10 tandem repeated GLP-1 analogs in yeast Pichia pastoris and its biological activity in a diabetic rat model.

Glucagon-like peptide-1 (GLP-1), an incretin secreted by intestinal L-cells, can effectively lower blood glucose levels in patients with diabetes. A fusion gene, consisting of 10 tandem repeated GLP-1 analog genes, was expressed at a high level in the yeast Pichia pastoris. SDS polyacrylamide gel electrophoresis (SDS-PAGE), and Western Blotting results showed that fusion protein migrated as a single protein band with a molecular weight of 36 kDa. A biological activity test showed that the GLP-1 analog could significantly lower the level of serum glucose when GLP-1 purified analog was injected into diabetic rats. A potential strategy for large-scale production of fusion protein containing the 10 GLP-1 analogs as discovered, and a single GLP-1 analog was obtained from fusion protein digested with trypsin. This should be inspired foreign expression of medicinal short peptides and be valuable in further research on GLP-1 analog drugs in the treatment of diabetes mellitus.

Oral administration of a fusion protein containing eight GLP-1 analogues produced in Escherichia coli BL21(DE3) in streptozotocin-induced diabetic rats.

Glucagon-like peptide-1 (7-36) amide (GLP-1), a gut hormone released into the blood stream after feeding, can stimulate insulin secretion by potentiating the insulinotropic action of glucose. An expression vector pET-22bG8, encoding a fusion protein containing eight tandem repeat GLP-1 ([Ser(8), Gln(26), Asp(34)]-GLP-1) analogues, was constructed and transformed into the Escherichia coli BL21(DE3) strain over-expressing the His-tagged fusion protein under the IPTG promoter. SDS-PAGE and Western blot analysis demonstrated that the His-tagged GLP-1 fusion protein migrated as a single protein with a molecular weight of 32 kDa. Following chronic (10 days) oral administration (20 mg kg(-1) day(-1)) of the fusion protein to diabetic rats, serum glucose levels were significantly lowered from 26 +/- 2.5 to 7.9 +/- 1.4 mmol/l. Further studies are needed to evaluate the potential use for GLP-1 analogue short peptide in the treatment of diabetes mellitus.

Growth promoting effect of a transgenic Bacillus mucilaginosus on tobacco planting.

In this study, we have investigated the plant growth promoting effect of Bacillus mucilaginosus strain D(4)B(1), a rhizosphere soil organism, and its transgenic strain NKTS-3 on tobacco planting. The transgenic strain contains a phytase expression cassette that can express high active phytase extracellularly and hydrolyze phytate in the soil to liberate inorganic phosphorus for the growth of tobacco plants. Greenhouse study and field experiments showed that both wild-type B. mucilaginosus and the transgenic strain could promote tobacco plant growth. Moreover, the transgenic strain promoted tobacco plant growth (235% more than control in pot experiments and 125% more than control in field experiments) was higher than the wild-type B. mucilaginosus (183% more than control in pot experiments and 108% more than control in field experiments). In addition, the inoculation with transgenic rhizobacteria could significantly improve root acquisition of phosphorus and increase the phosphorus content of the plant.