No abstract

In this study, the discrete element computational method (DEM) is applied to analyze the dynamic problems of an industrial cup brush in cleaning process. At first, the method was created in order to analyze the flows of granular materials, and then it has been developed to be able to model more complex objects like rods or beams of brittle, elastic or composite materials. The recently designed flexible rod model in this research is composed of spherical particles linked together to form an elastic rod-type object. Theoretical model and the simulation model will be expressed to draw out the result as the total slipped length of the brush, the total contact area, and acting forces between rod tips and surfaces in comparison with different rotary speeds. The analyzed results show that the slipped distance of a brush on surfaces and forces between brush tips and surfaces increase when the rotary speed is increased, while the total contact area are smallest at a certain rotary speed of 450 rpm, and this total area is larger when either increasing or decreasing the rotary speed. Hence the most effective cleaning speed in the current research is 900 rpm. It is possible to simulate and evaluate several different types of brushes to find the best model and compatible parameters for surface cleaning and polishing process by applying the DEM flexible rod model.

Cellulase is an important enzyme that plays a role in cleaving β-1,4 glucoside on cellulose to release glucose, which is of economic value and can be applied in many different fields. The 1545 bp endoglucanase gene mined from goat rumen's bacterial metagenomic data was expressed in Escherichia coli Rosetta2. In this study, the recombinant endoglucanase was purified by his-tag affinity chromatography with differrent processes, such as using phosphate buffer with or without sodium cloride, pretreatment of samples with ammonium sulphate before supplying into affinity column, using various concentration of imidazole for washing... Finally the endoglucanse was sucessfully purified by his-tag affinity column using sodium chloride-free phosphate buffer of which 150 mM and 400 mM imidazole were used for washing and enzyme elution, respectively. The resulting enzyme showed its high purity of 99%. CMC plate assay confirmed that although less active than commercial cellulase (Sigma), the recombinant cellulase hydrolyzed CMC to form a clear zone (halo) around the well. The purified enzyme is capable of using as material for further analysis.

Screening and expression of new β-glucosidase genes (bgc) have attracted much attention because of their valuable application in a wide range of industrial areas such as bioethanol production, food and animal feed processing, paper making, and biotechnological processes. Previously, we mined a new bgc gene coding for its mature enzyme (BGC) from metagenomic DNA data of bacteria in Vietnamese goats’ rumen. Based on the NCBI database, the BGC sequence was found to be the highest similarity with β-glucosidase of Bacteroidales bacterium (60.52%). The BGC enzyme was previously annotated to have two domains GH3 and GH31 and highly expressed in E. coli. The aim of this work was to experimentally confirm the predicted gene by expressing and assessing the activity of recombinant BGC from E. coli strains of BL21, Rosetta 1, C43, and SoluBL21. Furthermore, the expression level and solubility of the BGC were also investigated by varying fermentation conditions such as temperature, medium components, and IPTG concentration. The activity of the crude enzyme was identified through substrates including esculin and p-Nitrophenyl-β-D-glucopyranoside (pNPG). The new BGC could be used as potential material for further enzyme characterization.