ABSTRACT
Microbial transformation of benzaldehyde into L: -phenylacetylcarbinol by whole cell Saccharomyces cerevisiae has been carried out in a novel polyethylene glycol (PEG)-induced cloud point system. The system is composed of 80 g PEG 20,000, 75 ml Triton X-100, 20 g peptone, 10 g yeast extract, 25 g glucose, 1 g MgSO(4).7H(2)O, 0.05 g CaCl(2).2H(2)O, 35 g Na(2)HPO(4).12H(2)O, and 10.7 g citric acid per liter of tap water. The microbial transformation is conducted at 0.6 ml of acetaldehyde (35% volume content), 0.9 ml of benzaldehyde, and 7 g of wet cell per 100 ml of the PEG-induced cloud point system. Under the conditions, a relatively longer-term bioactivity of whole cell microorganism in the PEG-induced cloud point system has been achieved. A fed-batch microbial transformation process with a discrete addition of glucose and substrate gets a high final product concentration of about 8 g/l.
Subject(s)
Acetone/analogs & derivatives , Benzaldehydes/metabolism , Polyethylene Glycols/metabolism , Saccharomyces cerevisiae/metabolism , Acetaldehyde/metabolism , Acetone/metabolism , Biotransformation , Culture Media/chemistry , Glucose/metabolismABSTRACT
A novel polyethylene glycol-induced cloud point system (PEG-CPS) was developed for in situ extraction of moderate polar product by setting a microbial transformation of benzaldehyde into L-phenylacetylcarbinol (L-PAC) with Saccharomyces cerevisiae (baker's yeast) as a model reaction. The biocompatibility of the microorganism in PEG-CPS was comparatively studied with a series of water-organic solvent two-phase partitioning systems. The tolerance of microorganism to the toxic substrate benzaldehyde was increased and the moderate polar product L-PAC was extracted into the surfactant-rich phase in the PEG-CPS. The novel PEG-CPS fills the gap of in situ extraction of polar product in microbial transformation left by water-organic solvent two-phase partitioning system. At the same time, the application of PEG-CPS in a microbial transformation also avoids expensive solvent when compared with that of aqueous two-phase system or CPS.
Subject(s)
Acetone/analogs & derivatives , Benzaldehydes/metabolism , Polyethylene Glycols/metabolism , Saccharomyces cerevisiae/metabolism , Acetone/chemistry , Acetone/metabolism , Benzaldehydes/chemistry , Cell Survival , Glucose/chemistry , Glucose/metabolism , Molecular Structure , Polyethylene Glycols/chemistry , Saccharomyces cerevisiae/chemistry , Saccharomyces cerevisiae/cytologyABSTRACT
Triton X-45, a nonionic surfactant with a low hydrophile-lypophile balance value and dispersible in aqueous solution at room temperature, has a Krafft point above the room temperature. The cloud point of Triton X-45 in an aqueous solution is different from the conventional aqueous nonionic surfactant micelle solution. It was further confirmed by a determination of the effect of additives on the phase behavior of aqueous solutions containing Triton X-45. The experimental fact eliminates the prevalent concept that the cloud point of Triton X-45 is below room temperature, which is helpful to exploit a biocompatible medium for a microbial growth and then for whole cell microbial transformation in a nonaqueous medium.
