Front Plant Sci. 2015 Nov 24;6:1035.
Abstract
Bioconversion,
i.e., the use of biological systems to perform chemical changes in
synthetic or natural compounds in mild conditions, is an attractive tool
for the production of novel active or high-value compounds. Plant cells
exhibit a vast biochemical potential, being able to transform a range
of substances, including pharmaceutical ingredients and industrial
by-products, via enzymatic processes. The use of plant cell cultures
offers possibilities for contained and optimized production processes
which can be applied in industrial scale. Raspberry ketone
[4-(4-hydroxyphenyl)butan-2-one] is among the most interesting natural
flavor compounds, due to its high demand and significant market value.
The biosynthesis of this industrially relevant flavor compound is
relatively well characterized, involving the condensation of
4-coumaryl-CoA and malonyl-CoA by Type III polyketide synthase to form a
diketide, and the subsequent reduction catalyzed by an NADPH-dependent
reductase. Raspberry ketone has been successfully produced by
bioconversion using different hosts and precursors to establish more
efficient and economical processes. In this work, we studied the effect
of overexpressed RiZS1 in tobacco on precursor bioconversion to
raspberry ketone. In addition, various wild type plant cell cultures
were studied for their capacity to carry out the bioconversion to
raspberry ketone using either 4-hydroxybenzalacetone or betuligenol as a
substrate. Apparently plant cells possess rather widely distributed
reductase activity capable of performing the bioconversion to raspberry
ketone using cheap and readily available precursors.