Effects of Complex Enzymes Modification on Functional Properties of Soybean Protein Isolate Based on Orthogonal Experiment

Soybean protein isolate (SPI) is widely used in food industry because of its high protein nutritional function and good functional characteristics. However, due to the effect of amino acid composition and spatial structure on natural protein, its practical application is greatly limited. So it needs to be properly modified to meet the needs of production. In this study, SPI was used as substrate to explore the most suitable modification conditions by using complex enzymes (flavor protease, neutral protease, alkaline enzyme and transglutaminase) enzymolysis and then TG enzyme cross linking, in order to obtain SPI products with both solubility and gel as a special protein isolate for surimi products. The results show that: through the single factor experiment and orthogonal experiment, the optimized conditions of gel strength were determined: flavor protease: neutral protease: alkaline enzyme 1:1:2, pH 7, enzymolysis temperature 45°C, enzymolysis time 30 min. The optimized conditions of solubility: flavor protease: neutral protease: alkaline enzyme 1:2:2, pH 7, enzymolysis temperature 55°C, enzymolysis time 60 min. The result of orthogonal experiment: the optimized conditions was that flavor protease: neutral protease: alkaline enzyme 1:1:2, pH 7, enzymolysis temperature 55°C, enzymolysis time 60 min. The gel strength of products was 35.45 g, decreased 5.33% with control; Solubility was 36.24%, increased 54.01% with control. The modified SPI has excellent gel and solubility, and can be further applied to surimi products industry. And the results of this study provide a theoretical basis for its further application in surimi products.

The Characterization and Modification of a Novel Bifunctional and Robust Alginate Lyase Derived from Marinimicrobium sp. H1

Alginase lyase is an important enzyme for the preparation of alginate oligosaccharides (AOS), that possess special biological activities and is widely used in various fields, such as medicine, food, and chemical industry. In this study, a novel bifunctional alginate lyase (AlgH) belonging to the PL7 family was screened and characterized. The AlgH exhibited the highest activity at 45 °C and pH 10.0, and was an alkaline enzyme that was stable at pH 6.0–10.0. The enzyme showed no significant dependence on metal ions, and exhibited unchanged activity at high concentration of NaCl. To determine the function of non-catalytic domains in the multi-domain enzyme, the recombinant AlgH-I containing only the catalysis domain and AlgH-II containing the catalysis domain and the carbohydrate binding module (CBM) domain were constructed and characterized. The results showed that the activity and thermostability of the reconstructed enzymes were significantly improved by deletion of the F5/8 type C domain. On the other hand, the substrate specificity and the mode of action of the reconstructed enzymes showed no change. Alginate could be completely degraded by the full-length and modified enzymes, and the main end-products were alginate disaccharide, trisaccharide, and tetrasaccharide. Due to the thermo and pH-stability, salt-tolerance, and bifunctionality, the modified alginate lyase was a robust enzyme which could be applied in industrial production of AOS.

Combining Support Vector Machine with Dual g-gap Dipeptides to Discriminate between Acidic and Alkaline Enzymes

The catalytic activity of the enzyme is different from that of the inorganic catalyst. In a high-temperature, over-acid or over-alkaline environment, the structure of the enzyme is destroyed and then loses its activity. Although the biochemistry experiments can measure the optimal PH environment of the enzyme, these methods are inefficient and costly. In order to solve these problems, computational model could be established to determine the optimal acidic or alkaline environment of the enzyme. Firstly, in this paper, we introduced a new feature called dual g-gap dipeptide composition to formulate enzyme samples. Subsequently, the best feature was selected by using the F value calculated from analysis of variance. Finally, support vector machine was utilized to build prediction model for distinguishing acidic from alkaline enzyme. The overall accuracy of 95.9% was achieved with Jackknife cross-validation, which indicates that our method is professional and efficient in terms of acid and alkaline enzyme predictions. The feature proposed in this paper could also be applied in other fields of bioinformatics.

Studies on the Properties of Raw Flax and Hemp Fibres after Two Step Initial Treatment

The requirements regarding the properties of fibres are closely linked to their further application. The demands for garment and home textile considerably differ from requirements for fibres that are used for technical purposes. This paper presents the results on investigation of raw flax and hemp fibres after their initial treatment with two step method (cold or hot alkaline, enzyme treatment and bleaching as after-treatment). The properties of hemp and flax fibres are evaluated by colorimetric analysis, mechanical testing, and microscopy of the surface of fibres.

ACID AND ALKALINE INORGANIC PYROPHOSPHATASES IN SENESCING FLOWERS OF ROSE, CARNATION AND CHRYSANTHEMUM

The activities of the acid and alkaline inorganic pyrophosphatases (EC.3.6.1.1) were determined in the petals of cut flowers of roses (Rosa hybrida L.), carnations (Dianthus caryophyllus L.,) and chrysanthemums (Chrysanthemum morifolium (Ramat.)) kept either in water or in solutions of a flower preservative, and in flowers kept uncut on plants. The use of flower preservative decreased the activity of both pyrophosphatases in roses, did not change it in chrysanthemums, and maintained the alkaline enzyme at essentially the initial level in carnations. The activities of both enzymes were generally greater in the flowers of carnations and chrysanthemums than in roses, excepting the acid pyrophosphatase in uncut chrysanthemums on day 15, or the alkaline pyrophosphatase on days 15 and 17. The activities of both enzymes were essentially similar for each kind of flower indicating that their effect on anabolism or catabolism in flower petals was minimal.