Increased production of γ-lactones from hydroxy fatty acids by whole Waltomyces lipofer cells induced with oleic acid

Among several fatty acids tested, oleic acid was selected as the most efficient inducer for the production of 4-hydroxydodecanoic acid, a metabolite of β-oxidation, by Waltomyces lipofer. Cells were induced by incubation for 12 h in a medium containing 10 g l−1 yeast extract, 10 g l−1 peptone, 5 g l−1 oleic acid, 1 g l−1 glucose, and 0.05 % (w/v) Tween 80. The optimal reaction conditions for the production of γ-lactones by induced cells were pH 6.5, 35 °C, 200 rpm, 0.71 M Tris, 60 g l−1 hydroxy fatty acid, and 20 g l−1 cells. Non-induced cells produced 38 g l−1 γ-dodecalactone from 60 g l−1 10-hydroxystearic acid after 30 h, with a conversion yield of 63 % (w/w) and a productivity of 1.3 g l−1 h−1 under the optimized conditions, whereas induced cells produced 51 g l−1 γ-dodecalactone from 60 g l−1 10-hydroxystearic acid after 30 h, with a conversion yield of 85 % (w/w) and a productivity of 1.7 g l−1 h−1. The conversion yield and productivity of induced cells were 22 % and 1.3-fold higher, respectively, than those of non-induced cells. Induced cells also produced 28 g l−1 γ-decalactone and 12 g l−1 γ-butyrolactone from 60 g l−1 12-hydroxystearic acid and 60 g l−1 10-hydroxydecanoic acid, respectively, after 30 h. The concentration, conversion yield, and productivity of γ-dodecalactone and γ-decalactone are the highest reported thus far. This is the first study on the biotechnological production of γ-butyrolactone.