To cope with the bacteriophage problem for improvement of L-Phe production,we isolated bacteriophage BP-1 from the contaminated fermentation broth of E.coli WSH-Z06(pAP-B03) producing L-phenylalanine(LPhe).Through the treatment of WSH-Z06 with N-methyL-N'-nitro-N-nitrosoguanidine(NTG),selection for resistance to BP-1,transformation with plasmid pAP-B03,and examination for the capacity of L-Phe production,we obtained one mutant strain E.coli BR-42(pAP-B03).In the presence of BP-1,E.coli BR-42(pAP-B03) exhibited a satisfactory performance in cell growth and L-Phe production.It was confirmed that E.coli BR-42(pAP-B03) was a potential L-Phe over-producer against bacteriophage BP-1.It could be an excellent substitute for its parent strain WSH-Z06(pAP-B03) in L-Phe industry production.