Enhanced bioproduction of carvone in a two-liquid-phase partitioning bioreactor with a highly hydrophobic biocatalyst (original) (raw)
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Journal of Molecular Catalysis B: Enzymatic, 2002
Whole cells of Rhodococcus erythropolis DCL14 present carveol dehydrogenase (CDH) activity, which allows them to stereoselectively carry out the oxidation of the (+)-cis and (−)-trans-carveol to (+)-and (−)-carvone, respectively [1]. When a diastereomeric mixture of (−)-carveol was supplied for biotransformation, the (−)-trans-carveol was converted to (−)-carvone. When the cells grow on limonene or cyclohexanol the major activity is NAD-dependent. The relatively low water solubility of carveol and carvone was overcome through the implementation of an organic:aqueous system. The prolonged productivity of such a system depends on cell viability, since viable cells are naturally able to regenerate the co-factor. Fluorescence microscopy was used to off-line monitor cell viability during the time course of the biotransformation.
Applied Microbiology and Biotechnology, 2005
Carvone has previously been found to highly inhibit its own production at concentrations above 50 mM during conversion of a diastereomeric mixture of (−)-carveol by whole cells of Rhodococcus erythropolis. Adaptation of the cells to the presence of increasing concentrations of carveol and carvone in n-dodecane prior to biotransformation proved successful in overcoming carvone inhibition. By adapting R. erythropolis cells for 197 h, an 8.3-fold increase in carvone production rate compared to nonadapted cells was achieved in an air-driven column reactor. After an incubation period of 268 h, a final carvone concentration of 1.03 M could be attained, together with high productivity [0.19 mg carvone h −1 (ml organic phase) −1 ] and high yield (0.96 g carvone g carveol −1 ).
Tetrahedron Asymmetry, 2003
Rhodococcus opacus PW4 cells were found to produce trans-and cis-carveol and/or carvone as result of limonene metabolism, depending on the type and concentration of the carbon source used for cell growth. In aqueous systems, cells grown on ethanol and toluene only produced trans-carveol, whilst cells grown on limonene and on toluene with a larger head-space available produced both trans-carveol and carvone. In biphasic systems, limonene was converted to trans-and cis-carveol as well as to carvone, regardless of the carbon source used, although carveol and carvone production rates were higher in toluene and limonene grown cells, respectively. A good and stable emulsion was obtained in a magnetically stirred two-phase reactor but both trans-carveol and carvone were produced at low rates: 0.08 and 0.02 nmol/min mg prot, respectively. No cis-carveol was formed. When (−)-carveol was added, carvone production increased 4.7 fold to 0.12 nmol/min mg prot. Using an aerated two-phase reactor, carvone production was enhanced even with cells grown on toluene. The highest trans-and cis-carveol and carvone production rates were attained with cells grown on limonene by continuously supplying limonene to the reactor through the air stream, carvone production reaching 0.58 nmol/min mg prot. The best trans-/cis-carveol ratio (2.26) was observed with cells grown on toluene when limonene was supplied in the gas phase. When 50 mM limonene was added initially, carvone was produced 27.9 and 141.4 times faster than trans-carveol with cells grown on toluene and limonene, respectively.
Biodiesel production by transesterification of vegetable oils and animal fats is continuously growing, as well the production of crude glycerol raising the problem on how to dispose it in an economic and eco-friendly way. On the parallel, the demand of green chemicals, such as polyhydroxyalkanoa-tes (PHAs) and biosurfactants (BSs), is raising being a valuable economic perspective for new industrial process-es. Some bacteria are able to synthesize PHAs and BSs by different carbon sources, therefore crude glycerol may be a suitable source for green chemicals high-value added compounds. In this work biodiesl glycerol from Brassica carinata oil was converted into PHAs and BS by. Pseudomo-nas mediterranea 9.1.After a preliminar evaluation of its capability to use the main components of crude glycerol the growth efficiency was optimized by addition of either meat or yeast extracts. Then, by apply-ing a mathematical mechanistic model, nutritional requirements were defined and the influence...
Biotransformations in the Flavour Industry
Current Topics in Flavours and Fragrances, 1999
Bacteria and fungi synthesise or degrade a vast number of natural and xenobiotic substrates. Biotransformations and bioconversions occur, if a single substrate structure is altered by an identifiable redox, hydrolysis, or addition type reaction, or by a sequence of these reactions. Generally competing with chemosynthesis, biocatalysts possess inherent advantages: They functionalise chemically inert carbons, modify one functionality in a multifunctional molecule selectively or specifically, introduce chirality, resolve racemates, and operate under ambient conditions. The production of natural flavour and aroma ingredients could benefit from these characteristics. The biotransformation of volatile terpenes particularly well demonstrates perspectives, but also current problems. Solvent tolerant bacteria hold much promise for a lipophilic biotechnology. Genetic engineering will help to create tailor-made biocatalysts. Downstreaming of products, based on in situ solvent extraction or adsorption, is required for an efficient bioprocess. Cost calculations show that high-yielding biotransformations have commercial potential.
Biotechnology and Bioengineering, 2007
The biotransformation of toluene to 3-methycatechol (3MC) via Pseudomonas putida MC2 was used as a model system for the development of a biphasic process offering enhanced overall volumetric productivity. Three factors were investigated for the identification of an appropriate organic solvent and they included solvent toxicity, bioavailability of the solvent as well as solvent affinity for 3MC. The critical log P (log P crit) of the biocatalyst was found to be 3.1 and log P values were used to predict a solvent's toxicity. The presence of various functional groups of candidate solvents were used to predict the absorption of 3MC and it was found that solvents possessing polarity showed an affinity towards 3MC. Bis (2-ethylhexyl) sebecate was selected for use in the biphasic system as it fulfilled all selection criteria. A two-phase biotransformation with BES and a 50% phase volume ratio, achieved an overall volumetric productivity of 440 mg 3MC/L-h, which was an improvement by a factor of approximately 4 over previously operated systems. Additional work focused on reducing the toluene feed in order to minimize possible toxicity and decrease loss of substrate (toluene), a result of volatilization. Toluene losses were reduced by a factor of 4, compared to previously operated systems, without suffering an appreciable loss in overall volumetric productivity.
Biotransformations in two-liquid-phase systems
Enzyme and Microbial Technology, 1999
Phenylacetaldehyde can be obtained by oxidation of 2-phenylethanol with acetic acid bacteria in two-liquid-phase systems where the aldehyde is removed into the organic phase before its further conversion to acid. Two Acetobacter strains (ALEF and ALEG) were able to accumulate aldehyde when aliphatic hydrocarbons were used. A two-liquid-phase system, composed of water and isooctane (v/v, 1/1), was particularly suited for a significant accumulation of the aldehyde: Acetobacter sp. ALEG furnished 9 g/l of phenylacetaldehyde within 4 h starting from 10 g/l of alcohol and still 8 g/l were recovered after 24 h in the organic phase, whereas strain ALEF gave 3.5 g/l of aldehyde from 5.0 g/l of substrate. Acetobacter sp. ALEG also showed satisfactory long-term stability, being able to perform the transformation with 80% of the original activity after 3 days of contact with the solvent. Enzyme and Microbial Technology 25 (1999) 729 -735 0141-0229/99/$ -see front matter