Production of γ-decalactone from ricinoleic acid by immobilized cells of Sporidiobolus salmonicolor

Biotransformation of 12-hydroxystearic acid to gamma-decalactone: Comparison of two separation systems

Biotransformation of natural products to the natural flavoring, gamma-decalactone (GDL), has attracted considerable attention. However, improving its yield is challenging due to its high feedback inhibition of yeast cells, which lowers the productivity of the biotransformation process. In this study, we compared two in situ separation processes established by adding either resin (HZ-816) or cyclopentasiloxane (DC345) to a biotransformation medium and investigated their efficiency and effect on yeast metabolism. Compared with a control, yields from the medium with HZ-816 and DC345 increased by 140% and 175%, respectively. However, after 84 h of biotransformation, the protein leakage in the medium with HZ-816 and DC345 was respectively 2.04 times and 1.43 times that of the control. Meanwhile, the mortality of yeast cells was 32.8% and 24.0% in the medium with HZ-816 and DC345, respectively, whereas that in the control was 20.1%. Our findings indicate that a cyclase is involved in the final step of the biotransformation. The activity of the yeast cyclase in the DC345 system was 3.33 times greater than that in the HZ-816 system. The DC345 system was superior to the HZ-816 resin system in this separation process because its yield was 30.8% greater and it had less cellular damage. Thus, we showed that the DC345 system has potential as a new separation system for the production of GDL by biotransformation.

Bacterial Cellulose-Alginate Composite Beads as Yarrowia lipolytica Cell Carriers for Lactone Production

The demand for natural lactone gamma-decalactone (GDL) has increased in the fields of food and cosmetic products. However, low productivity during bioprocessing limits its industrial production. In this study, a novel composite porous cell carrier, bacterial cellulose-alginate (BC-ALG), was used for long-term biotransformation and production of GDL. The effects of this carrier on biotransformation and related mechanisms were investigated. BC-ALG carriers showed improved mechanical strength over ALG carriers, with their internal embedded cell pattern changed to an interconnected porous structure. In five repeated-batch biotransformation experiments, the maximum concentration of GDL obtained in culture with BC-ALG carriers was 8.37 g/L, approximately 3.7 times higher than that from the medium with an ALG carrier alone. The result indicated that multiple hydrogen bonding interactions at the interface between BC and ALG contributed to the compatibility and stability of BC-ALG carriers. On the basis of the above results, the BC-ALG composite carrier can be considered ideal for immobilisation of cells for the production of GDL on an industrial scale, and has the potential to be utilised in other biological processes.

Fed-batch versus batch cultures of Yarrowia lipolytica for γ-decalactone production from methyl ricinoleate

Constant medium feeding rate and intermittent fed-batch fermentation strategies were investigated aiming to increase the yields of γ-decalactone production by Yarrowia lipolytica, using methyl ricinoleate as substrate and ricinoleic acid source. The accumulation of another compound, 3-hydroxy-γ-decalactone, was also analyzed since it derives from the direct precursor of γ-decalactone thereby providing information about the enzymatic activities of the pathway. Both strategies were compared with the traditional batch mode in terms of overall productivity and yield in respect to the substrate. Although the productivity of γ-decalactone was considerably higher in the batch mode (168 mg l(-1) h(-1)), substrate conversion to lactone (73 mg γ-decalactone g(-1)) was greater in the intermittent fed-batch giving 6.8 g γ-decalactone l(-1). This last strategy therefore has potential for γ-decalactone production at an industrial level.

Preparation of Microbiological Agents for Organic Pollutants Removal in Wastewater

The authors have investigated the biochemical aspects of degradation processes of persistent organic compound benzothiazole by immobilized Rhodococcus rhodochrous cells, such as entrapped in Ca-alginate beads, or as being immobilized on some solid carries. The mineralization of toxicant was complete and biodestructive capacity of entrapped in alginate bacteria increased with each new experimental cycle.