Characterization of the interaction between allicin and soy protein isolate and functional properties of the adducts.

BACKGROUND: Soybean meal, a by-product of the soybean oil production industry, has a high protein content but the compact globular structure of the protein from soybean meal limits its wide application in food processing. Allicin has been found to have numerous functional properties. In this study, allicin was interacted with soy protein isolate (SPI). The functional properties of the adducts were investigated. RESULTS: Binding with allicin significantly quenched the fluorescence intensity of SPI. Static quenching was the main quenching mechanism. The stability of adducts decreased with increasing temperature. The greatest extent of binding between allicin and sulfhydryl groups (SH) of SPI was obtained at an allicin/SH molar ratio of 1:2. The amino groups of SPI did not bind with allicin covalently. Soy protein isolate was modified by allicin through covalent and non-covalent interactions. Compared with SPI, the emulsifying activity index and foaming capacity of adducts with a ratio of 3:1 were improved by 39.91% and 64.29%, respectively. Soy protein isolate-allicin adducts also exhibited obvious antibacterial effects. The minimum inhibitory concentrations (MICs) of SPI-allicin adducts on Escherichia coli and Staphylococcus aureus were 200 and 160 µg mL-1 , respectively. CONCLUSION: The interaction of allicin with SPI is beneficial for the functional properties of SPI. These adducts can be used in different food formulations as emulsifiers, foamers, and transport carriers. © 2023 Society of Chemical Industry.

The structure, antioxidant and antibacterial properties of thiol-modified soy protein isolate induced by allicin.

This study investigated the effect of allicin binding on the structure, antioxidant and antibacterial properties of soy protein isolate (SPI). Results showed that allicin bound to 82.6 % free thiol groups of SPI at a molar ratio of 0.5. The combination of allicin and SPI significantly affected the structure of protein. Result of circular dichroism showed that the content of α-helix decreased by 26.9 % and the content of ß-sheet increased by 12.2 % over control when the molar ratio was 0.5. The result of surface hydrophobicity signified the unfolding of SPI with the action of allicin. These results implied that allicin binding might be a suitable method for the modification of SPI. Furthermore, the antibacterialand antioxidant experiments indicated that allicin-SPI conjugates not only had the capacity to inhibit the growth of Escherichia coli and Staphyloccocus aureus, but also had DPPH and ABTS radicals scavenging activities.

Efficient genetic engineering of murine cochlear organoids.

Organoid culture is a popular model to study gene function as the easy manipulating and time saving compared with in vivo experiments. This is widely used in auditory system for studying supporting cells (SCs) or hair cells (HCs) as only very few SCs or HCs can be harvested in both human and murine cochlea. However, the use of organoids is still a challenge due to the low efficiency in genetic modification. Here we took Lin28b as an example and compared Lin28b gain-of-function (GOF) and loss-of-function (LOF) with different genetic engineering methods and found that TetOn induced GOF or LOF was more efficient compared with lipofection or lentiviral transduction in the experimental conditions we used. Cell apoptosis in TetOn induction system was lowest compared with the other methods in this study. Our study is the first to compare the efficiency of different genetic engineering techniques in cochlear organoid culture, which may also apply to organoids established with other tissues.

A thermal energy storage composite by incorporating microencapsulated phase change material into wood.

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix. The incorporation of MicroPCM and wood was realized using a vacuum impregnation method. The morphology and microstructure of MicroPCM, delignified wood (DLW) and PCESW were observed by scanning electron microscopy (SEM); the thermal properties including phase change temperature, enthalpy, thermal stability, thermal conductivity of MicroPCM and PCESW were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and laser flash analysis (LFA). The results showed that: (1) delignification improved the porosity of wood and enhanced the impregnation effect, MicroPCM got into the delignified wood successfully and mainly distributed in the vessels; (2) PCESW had excellent energy storage capacity and suitable phase transition temperature for regulating indoor temperature; (3) PCESW had prior thermal stability at room temperature and great durability after 100 heating-cooling cycles; (4) addition of graphene greatly improved the thermal conductivity of PCESW. The TES composite can be used as an indoor temperature regulating material for building energy conservation.

Secretory expression of nattokinase from Bacillus subtilis YF38 in Escherichia coli.

Nattokinase producing bacterium, B. subtilis YF38, was isolated from douchi, using the fibrin plate method. The gene encoding this enzyme was cloned by polymerase chain reaction (PCR). Cytoplasmic expression of this enzyme in E. coli resulted in inactive inclusion bodies. But with the help of two different signal peptides, the native signal peptide of nattokinase and the signal peptide of PelB, active nattokinase was successfully expressed in E. coli with periplasmic secretion, and the nattokinase in culture medium displayed high fibrinolytic activity. The fibrinolytic activity of the expressed enzyme in the culture was determined to reach 260 urokinase units per micro-liter when the recombinant strain was induced by 0.7 mmol l(-1) isopropyl-beta-D- thiogalactopyranoside (IPTG) at 20 degrees C for 20 h, resulting 49.3 mg active enzyme per liter culture. The characteristic of this recombinant nattokinase is comparable to the native nattokinase from B. subtilis YF38. Secretory expression of nattokinase in E. coli would facilitate the development of this enzyme into a therapeutic product for the control and prevention of thrombosis diseases.

[Effects of weak light stress on grain yield and photosynthetic traits of maize].

Through shading at 0-14 days before pollination (S1), 1-14 days after pollination (S2), and 15-28 days after (S3) pollination, this paper studied the effects of weak light stress on the grain yield and photosynthetic traits of maize cultivars FY3 and TY2. The results showed that all treatments of shading induced a decreased grain yield, among which, treatment S1 had the largest decrement, and FY3 was more sensitive to the shading. Weak light stress made the time of maximum grain-filling (Tmax) appeared later, grain-filling slowed down, and mass accumulation decreased. The earlier the weak light stress occurred, the later the Tmax appeared. During shading, the Chl (a + b) content, Chl a/b ratio, photosynthetic rate (Pn) as well as the photochemical efficiency (Fv/Fm) and actual quantum yield of PS II electron transport (phi(PS II)) in maize leaves decreased significantly, while the relative content of Chl b increased, and the intercellular CO2 concentration (Ci) and non-photochemical quenching (NPQ) increased markedly. After the shading ended, the Chl (a + b) content, Chi a/b ratio, Pn, Fv/Fm, phi (PS II), Ci, and NPQ restored gradually to the levels of non-shading, but the relative content of Chl b decreased, which suggested that non-stomatal limitation was part of the reason for the decreased Pn under weak light stress.

[Analysis of bacterial diversity of kefir grains by denaturing gradient gel electrophoresis and 16S rDNA sequencing].

Kefir is an acidic, mildly alcoholic dairy beverage produced by the fermentation of milk with a grain-like starter culture. These grains usually contain a relatively stable and specific balance of microbes that exist in a complex symbiotic relationship. Kefir grains can be considered a probiotic source as it presents anti-bacterial, anti-mycotic, anti-neoplasic and immunomodulatory properties. The microorganisms in Kefir grains are currently identified by traditional methods such as growth on selective media, morphological and biochemical characteristics. However, the microorganisms that isolate by these methods can not revert to Kefir grains which indicate that there are some other bacteria that are not isolate from it. In this study, PCR-based Denaturing gradient gel electrophoresis(DGGE) and sequence analysis of 16S ribosomal RNA gene (16S rDNA) clone libraries was used for the rapid and accurate identification of microorganisms from Kefir grains. The PCR primers were designed from conserved nucleotide sequences on region V3 of 16S rDNA with GC rich clamp at the 5'-end. PCR was performed using the primers and genomic DNAs of Kefir grains bacteria. The generated region V3 of 16S rDNA fragments were separated by denaturing gel, and the dominant 16S rDNA bands were cloned, sequenced and subjected to an online similarity search. Research has shown that regions V3 of 16S rDNAs have eight evident bands on the DGGE gel. The sequence analysis of these eight bands has indicated that they belong to different four genera, among them three sequences are similar to Sphingobacterium sp. whose similarities with database sequences are over 98%, three sequences are similar to Lactobacillus sp. whose similarities with database sequences are over 96%, the other two sequence are similar to Enterobacter sp., and Acinetobacter sp. whose similarities with database sequences are over 99% respectively. Although the DGGE method may have a lower sensitivity than the ordinary PCR methods, because when universal bacterial PCR primers are used, only the dominant microbiota of an ecosystem will be visualized on a DGGE gel, producing complex banding patterns. However, it could visualize the bacterial qualitative compositions and reveal the major species of the Kefir grains. Among them Sphingobacterium can be found in Kefir grains as the predominant flora which is reported for the first time. PCR-based DGGE and sequence analysis of 16S rDNA proved to be a valuable culture-independent approach for the rapid and specific identification of the microbial species present in microecosystem and probiotic products.

Purification and characterization of two novel antimicrobial peptides Subpeptin JM4-A and Subpeptin JM4-B produced by Bacillus subtilis JM4.

An antimicrobial peptides-producing strain was isolated from soil and identified as Bacillus subtilis JM4 according to biochemical tests and 16S rDNA sequence analysis. The corresponding antimicrobial peptides were purified to homogeneity by ammonium sulfate precipitation, sequential SP-Sepharose Fast Flow, Sephadex G-25 and C18 reverse-phase chromatography, and in the final purification step, two active fractions were harvested, designated as Subpeptin JM4-A and Subpeptin JM4-B. The molecular weights, determined by mass spectrometry, were 1422.71 Da for Subpeptin JM4-A and 1422.65 Da for Subpeptin JM4-B, respectively. Amino acid sequencing showed that they differed from each other only at the seventh amino acid except for three unidentified residues, and the two peptides had no significant sequence homology to the known peptides in the database, indicating that they are two novel antimicrobial peptides. In addition, characteristic measurements indicated that both peptides had a relatively broad inhibitory spectrum and remained active over a wide pH and temperature range.

[Food-grade gene expression systems for lactic acid bacteria].

Lactic acid bacteria (LAB) are important industrial microorganism used in the production and preservation of food-stuffs. Recently, considerable advances have been made in the genetics and molecular biology of LAB. These have resulted in the construction of food-grade gene expression systems for these bacteria. This paper aims to review the essential features for food-grade systems, food-grade selection markers, food-grade controlled gene expression and food-grade inducible signaling molecule, and recent developments on food-grade cloning and expression systems for LAB. These gene expression systems have great potential for studies on gene expression and regulation in LAB and a variety of bioprocessing application in industrial fermentations.