Juan Xu

Construction of the yeast whole-cell Rhizopus oryzae lipase biocatalyst with high activity

Surface display is effectively utilized to construct a whole-cell biocatalyst. Codon optimization has been proven to be effective in maximizing production of heterologous proteins in yeast. Here, the cDNA sequence of Rhizopus oryzae lipase (ROL) was optimized and synthesized according to the codon bias of Saccharomyces cerevisiae, and based on the Saccharomyces cerevisiae cell surface display system with α-agglutinin as an anchor, recombinant yeast displaying fully codon-optimized ROL with high activity was successfully constructed. Compared with the wild-type ROL-displaying yeast, the activity of the codon-optimized ROL yeast whole-cell biocatalyst (25 U/g dried cells) was 12.8-fold higher in a hydrolysis reaction using p-nitrophenyl palmitate (pNPP) as the substrate. To our knowledge, this was the first attempt to combine the techniques of yeast surface display and codon optimization for whole-cell biocatalyst construction. Consequently, the yeast whole-cell ROL biocatalyst was constructed with high activity. The optimum pH and temperature for the yeast whole-cell ROL biocatalyst were pH 7.0 and 40 °C. Furthermore, this whole-cell biocatalyst was applied to the hydrolysis of tributyrin and the resulted conversion of butyric acid reached 96.91% after 144 h.

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.

Optimization of the Freeze-Drying Media and Survival throughout Storage of Freeze-Dried Aerotolerant Bifidobacterium animailis Subsp. Lactis Qq08

The aim of the present work was to optimize the formula of cryoprotectants for freeze drying process of the previous selected Bifidobacteriumanimailis subsp.lactis Qq08 (Bl Qq08). Single factor and orthogonal experiments were conducted to optimize the cryoprotectants formula. The formula of cryoprotectants was optimized as follows: skim milk 15%, lactose 8%, Vc 1.5% and glycerol 3%. In the triplicate lyophilization tests, the average survival rate of Bl Qq08 reached 91.23%.The optimized formula of cryoprotectants was suitable for freeze drying of the Bl Qq08.

Research on Blanching Pretreatment of Quick Frozen Sword Bean (Canavalia gladiate)

Quick frozen could preserve the maximum micro-texture and taste quality of vegetables, and blanching pretreatment is primary determinant of quick frozen. In this study, the central composite experimental design and response surface methodology were adopted to derive a statistical model for the effect of blanching pretreatment on the quality of sword bean (Canavalia gladiate), with peroxidase activity as main index. The pretreatment process optimized with response surface methodology was blanching at 96 °C for 1.03 min. Through optimization, a statistical model was established for the relation between blanching temperature, time and peroxidase activity, which would facilitate the prediction of the effects of blanching on the quality of sword bean and could play a guidance role in the blanching pretreatment of many other vegetables.

Research on Quick Freezing Technology of Sword Bean (Canavalia gladiate)

Freezing technology has an important impact on the quality of quick frozen vegetables. In this study, followed blanching at 96.5 °C for 1.03 min, the effects of quick freezing of sword bean (Canavalia gladiate) on its quality were studied to optimize the quick freezing procedure. Electron microscope scanning was used to observe the microstructure, and maximum compressive strength and contents of vitamin C and chlorophyll were detected as well after quick freezing. The results showed that it was the optimized procedure to quick freeze sword bean was at-40 °C for 6.3 min, by which sword bean kept the best quality close to its fresh counterpart.

Construction of the Starter to Produce Lignocellulases via Solid State Fermentation of Rice Straw

The study demonstrates the starter construction and its solid state fermentation (SSF) using rice straw as substrate for lignocellulases production. The starter is constructed by natural microflora growing on rice straw additionally reinforced with Aspergillus niger ZJU-RYD1, using the SSF substrate rice straw with 90% moisture content, successfully produced the integrate and high active lignocellulases at about 72 h, i.e. CMCase 12.44 U/g, cellobiase 12.05 U/g, FPAase 3.18 U/g, xylanase 365.61 U/g, lassase 2.48 U/g. In this study the strategy is satisfactorily developed to construct the starter for high effective and low-cost production of lignocellulases using rice straw as substrate, based on natural microflora and additional reinforcing with special strain.

Construction of the Starter to Produce Lignocellulases via Solid State Fermentation of Metropolis Lignocellulosic Waste Defoliation

The study demonstrates the starter construction and its solid state fermentation (SSF) using metropolis lignocellulosic waste defoliation supplemented with wheat bran as substrates for lignocellulases production. The starter is constructed by natural microflora growing on defoliation additionally reinforced with Aspergillus niger ZJU-RYD1, using the SSF substrate defoliation with 90% moisture content, successfully produced the integrate and high active lignocellulases at about 120 h, i.e. CMCase 8.58 U/g, cellobiase 10.97 U/g, FPAase 2.21 U/g, xylanase 446.25 U/g, lassase 9.21U/g. In this study, the strategy is satisfactorily developed to construct the starter for high effective and low-cost production of lignocellulases using metropolis lignocellulosic waste defoliation as substrate, based on natural microflora and additional reinforcing with special strain