针对传统的蚂蚁算法容易出现早熟和停滞现象,提出一种新型蚂蚁算法(new ant colony algorithm,NACA),即将转移规则、全局信息素灾变规则和局部混合调整信息素规则。选择几个典型TSP问题进行实验。研究结果表明:新型蚂蚁算法一方面提高...针对传统的蚂蚁算法容易出现早熟和停滞现象,提出一种新型蚂蚁算法(new ant colony algorithm,NACA),即将转移规则、全局信息素灾变规则和局部混合调整信息素规则。选择几个典型TSP问题进行实验。研究结果表明:新型蚂蚁算法一方面提高了算法种群的多样性,同时将轮盘赌算子利用到城市转移规则中,有利于提高算法的收敛速度;另一方面,将种群个体的差分信息应用于局部信息素更新规则中,有利于搜索全局解;最后灾变算子避免算法陷入局部最优,而达到全局最优。新型的蚁群算法具有更强的搜索全局最优解的能力以及更好的稳定性和收敛性,同时为解决其他优化问题提供新的思路。展开更多
In the cultivation of gene engineered strain of Escherichia coli on glucose medium, excretion and accumulation of acetic acid inhibit not only cell growth but also the the expression of heterologous protein. It is obv...In the cultivation of gene engineered strain of Escherichia coli on glucose medium, excretion and accumulation of acetic acid inhibit not only cell growth but also the the expression of heterologous protein. It is obvious that the desirable host strain maintaining acetate at a low level is one of the approaches to increase the production of recombinant protein. The present article deals with the selection of mutants of E.coli DP19, DP8, which grow on the medium containing pyruvate as the sole carbon source in the presence of 50mmol/L fluoroacetic acid. It is shown that mutant DP19 is defective in its phosphotransacetylase(PTA)activity and accumulates less acetate in the medium, while DP8 is defective in acetate kinase (ACK)and accumulates similar level of acetate comparing with its parent. Using pta - mutant E.coli DP19 as host, the expression of GL 7ACA acylase gene on the recombinant plasmid pMR24 is improved, and the yield of enzyme activity in flask fermentation is about twice as much as its parent.展开更多
文摘针对传统的蚂蚁算法容易出现早熟和停滞现象,提出一种新型蚂蚁算法(new ant colony algorithm,NACA),即将转移规则、全局信息素灾变规则和局部混合调整信息素规则。选择几个典型TSP问题进行实验。研究结果表明:新型蚂蚁算法一方面提高了算法种群的多样性,同时将轮盘赌算子利用到城市转移规则中,有利于提高算法的收敛速度;另一方面,将种群个体的差分信息应用于局部信息素更新规则中,有利于搜索全局解;最后灾变算子避免算法陷入局部最优,而达到全局最优。新型的蚁群算法具有更强的搜索全局最优解的能力以及更好的稳定性和收敛性,同时为解决其他优化问题提供新的思路。
文摘In the cultivation of gene engineered strain of Escherichia coli on glucose medium, excretion and accumulation of acetic acid inhibit not only cell growth but also the the expression of heterologous protein. It is obvious that the desirable host strain maintaining acetate at a low level is one of the approaches to increase the production of recombinant protein. The present article deals with the selection of mutants of E.coli DP19, DP8, which grow on the medium containing pyruvate as the sole carbon source in the presence of 50mmol/L fluoroacetic acid. It is shown that mutant DP19 is defective in its phosphotransacetylase(PTA)activity and accumulates less acetate in the medium, while DP8 is defective in acetate kinase (ACK)and accumulates similar level of acetate comparing with its parent. Using pta - mutant E.coli DP19 as host, the expression of GL 7ACA acylase gene on the recombinant plasmid pMR24 is improved, and the yield of enzyme activity in flask fermentation is about twice as much as its parent.
