Isomalto-oligosaccharides (IMO) have good physiochemical properties and excellent physiological functions to make it widely used in food, medicine, feed, cosmetics and other industries. However, the procedures for industrial production of IMO are complicated. Therefore, it is necessary to develop an economical and easy-to-operate method. The genes encoding for β-amylase and α-transglucosidase were fused and co-displayed on the yeast cell surface of Yarrowia lipolytica which can convert liquefied starch to IMO in one step. The highest IMO purity of 75.3% was obtained using the displayed fusion-enzyme at 50 °C. This method showed potential application in IMO production.
Oligosaccharides ; Starch ; Yarrowia ; beta-Amylase

Genetic modification of barley variety can be an efficient way to improve beer quality. The objective of this study was to understand the effect of trxS gene on hydrolases activities in transgenic and non-transgenic barley seeds. The results showed that alpha-amylase, free beta-amylase and limit dextrinase activity were increased in transgenic seeds in comparison with non-transgenic seeds. Sulfhydryl content of protein in transgenic seeds was also higher than that in non-transgenic seeds, suggesting that trxS gene could express in barley seeds, which opens a new way for breeding new barley varieties to improve beer quality.
Germination ; genetics ; Glucosyltransferases ; metabolism ; Hordeum ; enzymology ; genetics ; Plants, Genetically Modified ; enzymology ; genetics ; Seeds ; enzymology ; genetics ; Sulfhydryl Compounds ; metabolism ; Thioredoxins ; genetics ; alpha-Amylases ; metabolism ; beta-Amylase ; metabolism

The effects of different timing of N fertilizer application at the same rate on grain beta-amylase activity, protein concentration, weight and malt quality of barley were studied. Grain beta-amylase activity and protein concentration were significantly higher in treatments where all top-dressed N fertilizer was applied at booting stage only or equally applied at two-leaf stage and booting stage than in the treatment where all top-dressed N fertilizer was applied at two-leaf age stage only. On the other hand, grain weight and malt extract decreased with increased N application at booting stage. There were obvious differences between barley varieties and experimental years in the grain and malt quality response to the timing of N fertilizer application. It was found that grain protein concentration was significantly and positively correlated with beta-amylase activity, but significantly and negatively correlated with malt extract and Kolbach index. The effect of grain protein concentration on malt quality was predominant over the effect of grain beta-amylase activity.
Agriculture ; methods ; Edible Grain ; chemistry ; drug effects ; metabolism ; Enzyme Activation ; Fertilizers ; Hordeum ; drug effects ; metabolism ; Nitrogen ; administration & dosage ; Plant Proteins ; metabolism ; Statistics as Topic ; Time Factors ; beta-Amylase ; chemistry ; metabolism

A beta-amylase gene (amyG) was cloned from a Bacillus megaterium WS06 and expressed in the Escherichia coli. Nucleotide sequence anlysis showed the amyG gene is composed of 1638 bp (545 amino acid residues with a Mr of 60.194 kD). The AmyG shows 94.5% sequence homologies with beta-amylase from Bacillus megaterium DSM319 and presents a normal beta-amylase primary structure, constituted by three parts: the N-terminal signal sequence, the catalytic domain and the C-terminal starch binding domains. The deduced amino acid sequence revealed that several highly conserved regions of the glycosylhydrolase family 14. The amyG gene was overexpressed using the pET21a vector and Escherichia coli BL21(DE3). The recombinant enzyme was purified 7.4 fold to electrophoretic homogeneity and had a Mr of 57 kD (by SDS-PAGE). The enzyme was optimally active at pH 7.0 and 60 degrees C and showed stability at the temperature below 60 degrees C. This enzyme efficiently hydrolyzed starch to yield maltose from non-reducing chain ends by exo-cleavage mode.
Bacillus megaterium ; enzymology ; genetics ; Cloning, Molecular ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism ; Sequence Analysis, Protein ; Sequence Homology, Amino Acid ; Temperature ; beta-Amylase ; biosynthesis ; genetics ; metabolism