Methods for microbial screening and production of polyol oils from soybean oil through bioprocess

Soypolyol oils (oxygenated acylglycerols) are important starting materials for the manufacture of polymers such as polyurethane. Currently, they are produced by a two-step chemical process involving epoxidation and the subsequent opening of the oxirane ring. The objective of this study is to develop a bioprocess to produce polyol oils directly from soybean oil. For product separation, we found that TLC with a two step development solvent systems could separate the polyol products from substrate soybean oil. The products and substrates were separated in the following order: substrate triacylglycerols (Rf 0.8), free fatty acids (FA, Rf 0.7), product dihydroxy TAG (Rf 0.4), trihydroxy TAG (Rf 0.3), monohydroxy FA (Rf 0.1) and dihydroxy FA (Rf 0.05). We also found that HPLC with a C18 reverse phase column and a linear gradient of 100% methanol to 100% 2-propanol over 60 min at 1 mL/min flow rate was able to separate product polyol oils and substrate soybean oil. Free FA and polyol oils (diacylglycerols (DAG) containing hydroxyl FA) were eluted between 5 min and 15 min. DAG containing two normal FA was eluted between 15 min and 28 min and the substrate soybean oil was eluted between 36 min and 45 min. A total of 400 microbial cultures were screened and we identified 25 hits. Polyol oils' products were purified through a silica gel column chromatography, fractionated by HPLC and then analyzed by MS. A total of 57 molecular species of DAG containing tri-, di-, monohydroxy FA and normal FA were identified by MS. HPLC chromatogram of evaporative light scattering detector was used for semi-quantification of these DAG in the purified polyol oils. The total content of the DAG containing two normal FA was about 25% and the total content of DAG containing hydroxy FA might be about 75%. The yield of bioconversion by culture A01-35 from soybean oil to polyol oil products (DAG containing hydroxyl FA) plus DAG containing normal FA was 31% by weight. Bioconversion of soybean oil to polyol oils is a new research area without available methodology to follow. Here we report a new bioprocess for the production of soypolyol oils directly from soybean oil.