FURTHER IMPROVEMENT OF D-BIOTIN PRODUCTION BY A RECOMBINANT STRAIN OFSERRATIA-MARCESCENS

We have previously reported that a recombinant strain of Serratia marc escens was constructed from a host released from feedback repression o f biotin biosynthesis and a recombinant plasmid carrying the mutated b iotin operon. To improve D-biotin production, we constructed a recombi nant plasmid pLGM304PA having the mutated biotin operon, a plasmid-sta bilizing element and the ampicillin resistant gene, and introduced it into the D-biotin producing strain ETA23K-8 which contained an additio nal copy of the mutated biotin operon and the kanamycin resistant gene , resulting in ETA23K-8(pLGM304PA). Studies of the growth conditions f or this recombinant strain indicated that high concentrations of sulph ur and ferrous iron were required for good production of D-biotin. A b atch culture fed by continuous addition of sucrose gave a maximum prod uction of 600 mg litre(-1).