Abstract
(1) An isoleucine auxotrophic mutant named No. 14-5 (ATCC No. 15940), derived from Brevibacterium flavum 2247 (ATCC No. 14067), produces a large amount of L-proline directly from sugar and inorganic nitrogen.
(2) The optimum concentration of L-isoleucine for the maximum production of L-proline is about 15mg/dl.
(3) Glucose and starch hydrolyzate are the most suitable carbon source for L-proline production, and 3-7%, especially 5.5%, of ammonium sulfate is the most favorable as inorganic nitrogen source. About 450μg/liter of biotin is necessary for abundant production of L-proline. Under these conditions, more than 1.2g/dl of L-proline is able to be produced in the medium from 10% glucose after shaking culture at 31° for 72hr.
(4) It is observed that the combination of three major chemical components, i.e., L-isoleucine, biotin, and ammonium sulfate, is very important for abundant production of L-proline. As the role of these components, the following conclusion was obtained.
(i) Some interrelation exists between isoleucine and proline biosynthesis.
(ii) High concentration of biotin serves to restrain extracellular glutamic acid production and, to increase proline production, as well as to promote the growth of this microorganism.
(iii) High NH+4 concentration, equivalent to 5.5% of ammonium sulfate against 10% glucose, is effective for increasing the accumulation of proline itself, as well as for decreasing by-product formation of alanine and valine.
