Biotransformation by plant cultures and microorganisms
Biotransformation by plant cultures and microorganisms is a good method
based on biotechnology for the preparation of volatile compounds that
have shown superior to compounds produced in cell cultures.
In biotransformation, an intermediate compound precursor is incorporated
into the culture medium, which is bio-transformed or bio-converted to
volatile compounds by enzymatic activities. The efficiency of this
method is much higher than those which a precursor is not used in the
culture medium. But it should be noted that cheap precursors should be
searched and used to produce valuable products [116]. For example,
10 mg/l vanillin was obtained on ferulic acid substrate by cultured
Capsicum annuum [139]. Citronellol can be obtained by
biotransformation of citronellal by the Peganum harmala [140]. Also
The biotransformation of ricinoleic acid by Candida sorbophila can
produce up to 40 g/l ץ-decalactone [141].
This method, in addition to positive aspects, also has negative aspects.
Such volatiles do not dissolve easily in aqueous medium. There are some
solutions to this problem agents facilitating dissolution can be used
(above a threshold concentration is inhibited cell growth). Even high
concentrations of the product itself can be toxic and inhibitory to
cells growth. As a result, continuous addition of substrate at
non-harmful concentrations and removal of the product were developed.
Among these methods, the pervaporation method [142] and inserting a
volatile binder compound is most commonly used. The issue of trapping
and isolating volatile compounds produced in the culture medium, has
been discussed by Georgiev et al [143] and Ramachandra and
Ravishankar [8]. For example, β-cyclodextrins are water-soluble
molecules with a hydrophobic interior and hydrophilic exterior that with
proper modification, can trap the product in their cavities.