No abstract

Biodiesel is increasingly perceived as an important component of solutions to the important current issues of fossil fuel shortages and environmental pollution. Utilization of soluble lipase offers an alternative approach to lipase-catalyzed biodiesel production using immobilized enzyme or whole-cell catalysis. Soluble lipase NS81020, produced by submerged fermentation of genetically modified Aspergillus oryzae microorganism, was first proposed here as the catalyst of biodiesel preparation with oleic acid in the biphasic aqueous-oil systems. The effect factors such as enzyme concentration, water content, temperature, molar ratio of methanol to oil, stirring rate and pH of buffer solution on the esterification rate were investigated systematically. The reaction time could be shortened with the increasing of enzyme concentration as long as the maximum enzyme absorptive capacity on the interface in the biphasic aqueous-oil systems was not achieved. The optimal water content in the biphasic aqueous-oil systems was 10 wt% by oleic acid weight. The reaction rate was enhanced with the increasing molar ratio of methanol to oil, the increasing stirring rate or the decreasing temperature. Although soluble lipase NS81020 had lower activity at pH 10.55, hydroxyl ion conduced to restrain hydrolysis of methyl ester and facilitated the reaction toward the methyl ester formation.

This paper investigates the finite‐time consensus problem for multi‐agent systems with second‐order individual dynamics under switching topologies. A distributed continuous‐time protocol is designed to guarantee finite‐time consensus for homogeneous agents without predetermined leaders, i.e., it ensures agents asymptotically converge to an average consensus within finite time, even if the interaction topology among them is time‐varying but stepwise jointly‐connected. In particular, it introduces a distributed continuous‐time protocol to reach consensus in finite time and reduce the chattering together. Finally, the simulation results are also given to validate the proposed approach.

No abstract

Based on recent literary sources, this survey discusses the effects of main factors influencing the microbial-induced calcium carbonate precipitation (MICP), including the bacterial species, bacterial concentration, temperature, and pH value. While the MICP technology has been widely adopted to improve rock and soil characteristics, it has excellent development prospects in many other fields. The breakthrough solutions in the MICP technology are improving geotechnical and foundation sand properties, repairing cement-based materials, using mineralized film mulching to protect cultural relics, enhancing properties of tailings, desert control, and heavy metal environmental restoration, etc., are discussed. The experimental findings prove that MICP can improve the strength, stiffness, liquefaction resistance, erosion resistance, and permeability of geotechnical materials and maintain the good permeability and permeability of the soil and improve the growth environment of plants. It is an environment-friendly bioengineering technology. Because microbial mineralization involves a series of biochemical and ionic chemical reactions, there are many reaction steps in the solidification process and the solidification effect of MICP is restricted and affected by many factors. The comprehensive analysis and optimization strategy on MICP industrial implementation should account for micro- and macro-scale effects: the type of bacteria, the concentration of bacteria and cementation solutions, ambient temperature, pH value, and other factors directly affect the crystallization type, morphology, and size of calcium carbonate from the microscopic standpoint, while the macro-scale factors control the rock and soil mineralization. The limitations and prospects of the MICP technology are outlined.