NOVELTY - Recombinant Escherichia coli comprises wild strain BW25113 for encoding isocitrate dehydrogenase phosphatase or kinase aceK, and gene is deleted to obtain mutant strain of Escherichia coli i.e. BW delta aceK. The anaerobic induction of plasmid pETA is selected. The caiBCD fragment is inserted in NdeI/KpnI cleavage site in multiple cloning site to obtain first over-expression plasmid pEH-caiBCD. The caiT inserted is into pACYCD NdeI/XhoI site, caiF into pACYCD Hind III/EcoR I sites to obtain second over-expression plasmid pACYCD-caiT-caiF.    USE - Recombinant Escherichia coli for producing L-carnitine (claimed).    ADVANTAGE - The recombinant bacteria Escherichia coli enables to produce high yield L-carnitine from crotonobetaine that has high substrate efficiency in simple, economical and eco-friendly manner.    DETAILED DESCRIPTION - Recombinant Escherichia coli comprises wild strain BW25113 for encoding isocitrate dehydrogenase phosphatase or kinase aceK, and gene is deleted to obtain mutant strain of Escherichia coli i.e. BW delta aceK. The anaerobic induction of plasmid pETA is selected. The caiBCD fragment is inserted in NdeI/KpnI cleavage site in multiple cloning site to obtain first over-expression plasmid pEH-caiBCD. The caiT inserted is into pACYCD NdeI/XhoI site, caiF into pACYCD Hind III/EcoR I sites to obtain second over-expression plasmid pACYCD-caiT-caiF. The two over-expression plasmids pEHcaiBCD and pACYCD-caiT-caiF are simultaneously transformed into Escherichia coli mutant BW delta aceK to obtain produce L-carnitine. INDEPENDENT CLAIMS are included for:    (1) a method for producing recombinant Escherichia coli, which involves taking wild strain of Escherichia coli BW25113, and deleting aceK gene to obtain mutant strain of Escherichia coli BW delta aceK;    (2) designing forward and reverse primers for amplifying CaiBCD, caiF and caiT fragments, where caiF forward primer and reverse primer comprises 34 and 33 nucleobases (SEQ ID NOs: 3and 4), and caiT forward primer and reverse primer comprises 34 nucleobases (SEQ ID NOs: 5and 6), given in the specification;    (3) selecting anaerobically induced promoter plasmid pET-A as the carrier, obtaining pEH-caiBCD and pACYCD-caiT-caiF plasmids; and transforming in Escherichia coli; and    (4) a method for producing L-carnitine, which involves amplifying recombinant bacteria for preparing whole cell enzyme source, connecting enzyme-producing culture medium BW delta aceK/pEH-caiBCD ans pACYCD caiT-caiF, culturing aerobically and then anaerobically, centrifugation at 0-10 degrees C and 8000-12000 revolution per minute, collecting cells, washing cells with 10-100mmol/l phosphate buffer, preparing conversion reaction solution containing crotonobetaine substrate, adding bacterial culture having cell concentration 10-50g/l, and pouring reaction mixture into shaker.