40results about How to "Improve the stability of enzyme activity" patented technology

The invention discloses a mutant of D-amino acid oxidase, the sequence of which comprises amino acid residue N at position 54 of the sequence shown in SEQ ID NO.1 or a sequence having at least 76% identity with SEQ ID NO.1, The mutated sequence of the 58th amino acid residue F, the 211th amino acid residue C and the 213th amino acid residue M; the D-amino acid oxidase mutant has a higher enzyme than the wild-type D-amino acid oxidase activity, enzymatic stability and / or ammonium resistance. The invention also discloses the application of the D-amino acid oxidase mutant in the preparation of 2-oxo-4-(hydroxymethylphosphinyl)butyric acid. The D-amino acid oxidase mutant of the present invention has high enzyme activity, improved enzyme activity stability and / or enhanced ammonium resistance, thereby reducing costs and being beneficial to industrial production.

The invention relates to a glutamate decarboxylase mutant with improved thermal stability and an application thereof, belonging to the field of bioengineering. The mutant is prepared primarily by the following steps: performing saturated mutation of glutamine Q, valine V and threonine T on the sites 5-7 of the amino acid sequence of glutamate decarboxylase, and screening to obtain high-stability mutants Q5E / V6S / T7V, Q5Y / V6R / T7K and Q5N / V6Y / T7V. In the glutamate decarboxylase mutant prepared in the invention, the half-inactivation temperature is 45-50.5 DEG C which is 4.9-10.2 DEG C higher than that of wild type mutant; and the half-life period at 45 DEG C is 76-129min, which is 3.2-4.3 times higher than 24min of wild type mutant. By transforming glutamic acid for 12h with the whole cell of glutamate decarboxylase mutant synthesized from recombinant escherichia coli, 260-350g / L gamma-aminobutyric acid (GABA) can be obtained, and the molar yield is 76.6-97.8%. In the glutamate decarboxylase mutant prepared in the invention, the thermal stability is obviously improved, the production of gamma-aminobutyric acid is facilitated, and a foundation is laid for efficient synthesis of gamma-aminobutyric acid.

The invention discloses a high-activity peanut shell polysaccharide and a preparation method thereof and belongs to the technical field of natural product preparation. Mutants of an endoglucanase and a cellobiohydrolase are obtained by a site-directed mutation way, compounding is performed, and an active polysaccharide and a flavonoid compound are synchronously obtained from peanut shells by an ultrasonic assisted enzymolysis and extraction way. The optimum hydrolysis temperature and enzyme activity of the complex enzymes are improved by the complex enzymes and the preparation process, operation steps are simplified, extraction time is reduced, synchronous preparation of the flavonoid compound and the water-soluble polysaccharide from peanut shells is realized, synchronous enzymolysis and extraction of the polysaccharide under a medium-high temperature condition is also realized, the obtained active polysaccharide is high in flavonoid content, and strong in antioxidant activity and antibacterial activity, and has a plurality of physiological functions and a wide application range.

The invention discloses a beer liquid compound enzyme and a preparation method thereof and belongs to the technical field of preparation of liquid compound enzymes. According to the beer liquid compound enzyme, a liquid enzyme preparation for beer brewage is taken as a main raw material, stabilizers such as sugar, polyhydric alcohol, an amino acid, a thickener, albumin, metal ions and the like as well as substances such as a hop extract, a Chinese herbal medicine extracting solution, antibacterial peptides and the like which have anti-corrosion effects and can promote the enzyme preparation to be more stable are compounded scientifically, and the addition of a preservative is completely replaced, so that the breeding and the growth of harmful microorganisms are effectively inhibited, the activity of the liquid compound enzyme can be stabilized synergistically together with other components, the biological stability and the enzyme activity stability of the liquid compound enzyme are improved fundamentally, and the shelf life of the liquid enzyme preparation is effectively prolonged. The total number of bacterial colonies is in a range of 168-214 CFU / mL if the prepared liquid compound enzyme is stored at the room temperature for 12 months; enzyme activity loss ratios are in ranges of 2-2.5% and 1-1.7% respectively if the prepared liquid compound enzyme is stored at temperatures of 40 DEG C and 0 DEG C for 12 months.

The invention relates to novel high-temperature resistant alpha-amylase, a preparing method of the novel high-temperature resistant alpha-amylase and an application of the novel high-temperature resistant alpha-amylase. As PCR site-specific mutagenesis is carried out on genes of wild-type high-temperature resistant alpha-amylase, and the genes are efficiently expressed in bacillus subtilis. The novel high-temperature resistant alpha-amylase is high in stability in the high-temperature environment and the acid environment, and can better adapt to industrial production to achieve the effects of saving energy, reducing consumption and improving efficiency. By means of the technical scheme, the genes of the wild-type high-temperature resistant alpha-amylase are separated from bacillus licheniformis, mutagenesis is carried out on His316 amino acid residues of the genes, efficient expression is carried out in the bacillus subtilis, and under the 90-DEG C condition and the pH-4.5 condition, the stability of the novel high-temperature resistant alpha-amylase (His316 to Arg) is improved compared with the wild-type high-temperature resistant alpha-amylase.

The invention relates to genetic engineering field, in particular to eosinophilic lactase BGALA, gene and application thereof. The invention provides a lactase BGALA of eosinophilic Bispora sp.; the amino acid sequence of the lactase BGALA is shown in SEQ ID NO.1; and the invention provides genome and cDNA coding gene bgalA for coding the lactase. The invention obtains an eosinophilic lactase with the most proper pH value of 1.5, which maintains high enzymatic activity in acid environment, has better pH stability and heat stability, and antiprotease hydrolysis. The eosinophilic lactase can effectively hydrolyze the lactose in milk in simulated digestive tract environment. The eosinophilic lactase BGALA with the properties can be used for treating lactose intolerance, diary industry no processing cow milk and whey.