Guo Qing He

Response surface methodology for optimizing the fermentation medium of alpha-galactosidase in solid-state fermentation.

Aims:  Alpha‐galactosidase is applied in food and feed industries for hydrolysing raffinose series oligosaccharides (RO) that are the factors primarily responsible for flatulence upon ingestion of soybean‐derived products. The objective of the current work was to develop an optimal culture medium for the production of alpha‐galactosidase in solid‐state fermentation (SSF) by a mutant strain Aspergillus foetidus.

Construction of a Yeast Cell-Surface Display System and Expression of Trametes sp. laccase

Laccases (1.10.3.2, p-diphenol: dioxygen oxidoreductases) is a family of blue copper-containing oxidases that are commonly found in bacteria, fungi and plants. It is able to oxidize and degrade a variety of aromatic compounds and other organic compounds. Due to this ability, laccases can serve environmental bioremediation processes and industrial purposes. Cell-surface display of enzymes is one of the most attractive applications in yeast. It is a effective utilization to construct the whole cell biocatalyst. The cDNA sequence of Trametes sp. C30 LAC3 was optimized and synthesized according to the codon bias of Saccharomyces Italic textcerevisiae, because codon optimization has been proved to be effective to maximize production of heterologous proteins in yeast. The genes encoding galactokinase (GAL1) promoter, α-mating factor 1 (MFα1) pre-pro secretion signal, fully codon-optimized LAC3, the 320 amino acids of C terminal of α-agglutinin, alcohol dehydrogenase (ADH1) terminator and kanMX cassette were amplified and cloned into YEplac181 to construct a cell-surface display vector called pGMAAK-lac3 with α-agglutinin as an anchor. Then pGMAAK-lac3 was transformed into S. cerevisiae. The results show LAC3 was immobilized and actively expressed on S. cerevisiae. However, the substrate specifity and activity were obviously changed. The displayed LAC3 lost the activity to phenolic substrate (guaiacol) and its activity to non-phenolic substrate (ABTS) was greatly reduced. To our knowledge, this was the first attempt to construct and express laccase through cell-surface display technology.

Application of a Novel Freeze-Dried Aerotolerant Bifidobacterium animailis Subsp. Lactis Qq08 (Bl Qq08) in Probiotic Yoghurt Production

Probiotics are of great beneficial functions, especially on gastrointestinal health. Probiotic yoghurt is gaining popularity for it is the main way to supplement probiotics. In this study, a novel probiotic yoghurt was made by adding a freeze-dried aerotolerant Bifidobacterium animailis subsp. lactis Qq08 (Bl Qq08) to traditional yoghurt. Microbial, physical, chemical and flavor changes of the yoghurt during cold storage were analyzed weekly to study the effects of Bifidobacterium addition on the yoghurt quality. Results showed that the addition of Bl Qq08 didn’t significantly affect the cell viabilities in yoghurt which kept above the recommended level. Chemical and flavor characteristics of the probiotic yoghurt kept similar or turned better, indicating that the lyophlized Bl Qq08 was an excellent probiotic bacteria to product yoghurt.

Analysis of the Volatile Compounds in Chinese Steamed Bread Packaged by PA/CPP Material

PA/CPP packaging material was used for Chinese steamed bread to evaluate its ability to improve quality and increase steamed bread shelf-life. The changes on the aroma volatiles during storage were assessed using by simultaneous distillation extraction(SDE) with dichloromethane and were analysed by GC-MS. The obtained results showed that there were 17 volatile components in fresh Chinese steamed bread, however, after 3 days of storage at 4°C tempreture, the flavor compounds significant decreased in the steamed bread without packaged, only 6 volatile components could be determinted. For the PA/CPP group storged at 4°C tempreture after 3 days, there were 21 volatile components identified, and most of components were the same to the fresh steamed bread.

The Screening of Optimal Ganoderma lucidum and the Effect of Medium Substrate on Bioactive Metabolite in Submerged Culture

To determine an optimal G. lucidum strain, we made the production of mycelia biomass, EPS, IPS, IT, ET as indicators, among the five tested strains, the American G. lucidum was screened, and the production of mycelia biomass, EPS, IPS, IT, ET could reach 2.013g/100 ml, 11.2988 mg/100ml, 23.7800 mg/10ml, 45.5412 mg/100ml, 11.1417 mg/100ml, respectively. On the other hand, according to the screening of carbon and nitrogen sources as well as their concentration, the suitable carbon and nitrogen was 3% malt powder, 1.5% yeast extract. So we can use the fermentation culture for the following research, which was as follows：3% malt powder, 1.5%yeast extract, 0.3% KH2PO4, 0.15% MgSO4, 0.005% VB1.

Influence of the Quality of Soy Sauce after Replacing the Salt with the Secondary Pickled Vegetable Bittern in its Fermentation

The bittern soy sauce was investigated. Two kinds of the vegetable bittern –the mustard tuber and potherb mustard were added in the fermentation respectively. After the fermentation, physical, chemical and sensory quality attributes were monitored. As a result, the physicochemical property was not influenced significantly by the vegetable bittern and the free amino acids were higher. The soy sauce was proved to be consistent with the standard.

Solid-State Fermentation Production of α-Galactosidase by Aspergillus niger Zju-Y1

The agro-byproduct culture medium for α-galactosidase production by Aspergillus niger zju-Y1 was optimized with flask-SSF via response surface methodology, maximum α-galactosidase yield at the level of 230.159 U/g dry matter was achieved by using wheat bran and soybean meal as culture medium components. Furthermore, based on the flask-SSF results, the three-section-control strategy was developed for scale-up SSF, making fermentation steadily and efficiently, and the α-galactosidase activity hitting to 174.410 U/g dry matter, which is close to the result of flask-SSF. The results demonstrated that a feasible scale-up SSF mode for α-galactosidase production is successfully set up by combining the utilization of agro-byproduct culture medium and three-section-control strategy.

Improved Water-Solubility of Phytosterol by Hydroxypropyl-β-Cyclodextrin

Phytosterol has been shown to lower the serum cholesterol concentrations, but its low solubility in water restricts its application. In this study, hydroxypropyl-β-cyclodextrin was used to improve the water-solubility of phytosterol. Phase solubility study pointed out the formation of 1:1 inclusion complexes between phytosterol and hydroxypropyl-β-cyclodextrin. The initial dissolution rate was remarkedly improved in the first two minutes. The suitable solvent and temperature for complex formation was n-butanol and 40°C.

Correlation Analysis between Biomass and Extracellular Alpha-Galactosidase Activity of Pediococcus acidilactici XS1B

Many mathematical models can be used to optimize the fermentation process, and predict the harvest of products, but most of them only applied in the biomass factor, not the activity of enzymes, especially inducing enzyme such as α-galactosidase. In this study, Pediococcus acidilactici XS1B was incubated and measured by two periods: 48h with interval of 2h, 9d with interval of 1d. After analyze data of active bacteria amounts, biomass, catalyst activity, 2 pairs correlation were established: the active bacteria amounts with biomass increasing rate is 0.461, the biomass and catalyst activity is 0.935. With this correlation, the models used to measure biomass can also fit to α-galactosidase activity.

The Preparation of a Hyper-Thermostable Whole-Cell Biocatalyst and its Application for Biosynthesis of Biodiesel

In this study, a hyper-thermostable lipase whole-cell biocatalyst has been developed. The hydrolytic activity of the codon-optimized ROL displayed on the yeast cell surface was 19.5 U /g dried cells cultured in SD medium, while the biomass was 13 g/L. Moreover, the whole-cell biocatalyst presented great thermostability. After 10 min incubation at 90 °C, 95 °C and 100 °C, the residual activity of lipase still remained 89%, 86% and 68%, respectively. Therefore, the whole-cell biocatalyst was applied in bioconversion of FAME and biodiesel. In our study, 50 mM oleic acid was most reasonable for bioconversion of FAME, and 50 mM soy oil was most reasonable for bioconversion of biodiesel, when the reaction were carried out in hexane as the solvent, and the molar ratio of oleic acid (or soy oil) and methanol was 1:4. Reactions were catalyzed by 0.5 g lyophilized bioimprinted whole-cell biocatalyst and incubated at 45 °C for 12 h with shake.