Comparison of the Δ^(12) fatty acid desaturase gene between high-oleic and normal-oleic peanut genotypes

△^12 fatty acid desaturase gene has been targeted as a logical candidate controlling the high oleate trait in peanut seeds. By RT-PCR method, the full-length cDNAs of △^12 fatty acid desaturase gene were isolated from peanut （Arachis hypogaea L.） genotypes with normal and high ratio of oleic to linoleic acid, which were designated AhFAD2B and AhFAD2B＇, respectively. Sequence alignment of their coding regions revealed that an extra A was inserted at the position ＋442 bp of AhFAD2B＇ sequence of high oleic acid genotypes, which resulted in the shift of open reading frame and a truncated protein AhFAD2B＇, with the loss of one histidine box involved in metal ion complex required for the reduction of oxygen. Analysis of transcript level showed that the expression of △^12 fatty acid desaturase gene in high oleic acid genotype was slightly lower than that in normal genotype. The enzyme activity experiment of yeast （Saccharomyces cerevisiae） cell transformed with AhFAD2B or AhFAD2B＇ proved that only AhFAD2B gene product showed significant △^12 fatty acid desaturase activity, but AhFAD2B＇ gene product did not. These results suggested that the change of AhFAD2B＇ gene sequence resulted in lower activity or deactivation of △^12 fatty acid desaturase in high oleic acid genotype.

Screening of High Temperature Resistant Fodder Yeast Strains

[ Objective] This study aimed to screen yeast strains suitable for high temperature processing of formulated biological feed. [ Method ] High temperature resistance and culture conditions of six yeast strains were investigated. [Result] Two yeast strains resistant to high temperature （45 ℃ ） with high viable cell number （10^8 cells/ml） were screened, including DQFC2117-1 and DQFC2122-2. [ Conclusion] Strains DQFC2117-1 and DQFC2122-2 could be used as high temperature resistant yeast strains for processing of formulated biological feed.

Sucrose enhances the chromogenic ability of Staphylococcus xylosus by improving nitric oxide synthase activity

In this paper,the effect of different concentrations of sucrose stress on color formation of the Staphylococcus xylosus was investigated.The results showed that the highest a*value and the best coloring effect similar to those of nitrite were observed after the addition of 0.05 g/mL sucrose to stress the S.xylosus.UV-Vis and electron spin resonance spectra analysis showed that production of coloring product Mb-NO was significantly enhanced after 0.05 g/mL sucrose stress.The growth curve,reactive oxygen content,cell cycle,nitric oxide synthase(NOS)activity,zeta potential,cell size,and protein composition of S.xylosus were investigated to reveal the mechanism of sucrose stress to enhance the coloring effect of the strain.The result showed that sucrose inhibited the growth of S.xylosus,which changed the physiological state by activating the oxidative stress response.The stress altered the rate of intracellular metabolism of S.xylosus by delaying the cell cycle and increasing cell surface zeta potential and cell particle size.These changes altered the protein composition of the cells and significantly enhanced the activity of intracellular NOS,which could improve the chromogenic ability of S.xylosus.This study will provide theoretical support for sucrose stress on S.xylosus to enhance its coloring effect,and sucrose stress for S.xylosus might be a promising biological alternative to nitrite in meat products.

A review:antimicrobial properties of several medicinal plants widely used in Traditional Chinese Medicine

Introduction Due to the dramatic increase in the use of antibiotics and growing health threat of bacterial resistance to many commonly used antibiotics,many studies have been directed at developing new and effective antibacterial compounds,among which many new,natural,and effective antibacterial compounds discovered from medicinal plants have drawn great interest and raised new hope for treating the challenges of antibiotic resistance.This review aimed to summarize the most important and widely used medicinal plants that were reported to have antibacterial activities.A general literature search from 2010 to 2020 was conducted using different databases,including Science Direct,Web of Science,and PubMed.According to the literature,three medicinal plants with outstanding antibacterial activities,Taraxacum officinale,Coptis Rhizome,and Scutellaria baicalensis,were screened and reviewed by prioritization.The extraction methods,antibacterial activities of different parts of plants or the plant-derived compounds,spectra of antibacterial activities,and toxicity were described,respectively.However,the antibacterial activities of the extracts or pure compounds as reported in the reviewed literature were mostly based on in vitro assays,and moreover,the deeper antibacterial mechanisms have not been elucidated clearly.Therefore,further studies are required in the fields of purification and identification of the antibacterial compounds,its mechanisms of action,and synergistic effects in combination with other antibacterial drugs,which may be helpful in the development of new antibacterial drugs.

Quantum dot biosensor combined with antibody and aptamer for tracing food-borne pathogens

Due to the increasing number of food-borne diseases,more attention is being paid to food safety.Food-borne pathogens are the main cause of food-borne diseases,which seriously endanger human health,so it is necessary to detect and control them.Traditional detection methods cannot meet the requirements of rapid detection of food due to many shortcomings,such as being time-consuming,laborious or requiring expensive instrumentation.Quantum dots have become a promising nanotechnology in pathogens tracking and detection because of their excellent optical properties.New biosensor detection methods based on quantum dots are have been gradually developed due to their high sensitivity and high specificity.In this review,we summarize the different characteristics of quantum dots synthesized by carbon,heavy metals and composite materials firstly.Then,attention is paid to the principles,advantages and limitations of the quantum dots biosensor with antibodies and aptamers as recognition elements for recognition and capture of food-borne pathogens.Finally,the great potential of quantum dots in pathogen detection is summarized.