Enzymatic synthesis of green notes with hydroperoxide-lyase from olive leaves and alcohol-dehydrogenase from yeast in liquid/gas reactor

Hydroperoxide-lyase is a suitable enzyme for the biocatalytic production of six-carbon aldehydes which are responsible for the “green notes” in many fruits and vegetables. The hydroperoxide-lyase isolated from olive leaves is used in this work. The effects of pH, temperature, and substrate and enzyme concentrations on hexenals generation were optimized. The main objective of this paper consists on the elaboration of a biocatalytic procedure for the synthesis of flavors with green odor characteristics. For this purpose an enzymatic liquid/gas reactor, where the synthesis of C6-compounds was coupled to their extraction, has been proposed. Hexenals were produced in two steps: (1) 13 hydroperoxy-linolenic acid was produced from hydrolyzed linseed oil in presence of soybean lipoxygenase. (2) 3Z- and 2E-hexenals (up to 0.36 g kg⁻¹ of reaction medium) were produced from 13 hydroperoxy-linolenic acid in presence of olive hydroperoxide-lyase at 50% yield. The hexenals were successfully reduced into their corresponding alcohols by adding yeast cells Saccharomyces cerevisiae containing alcohol-dehydrogenase activity to the same reactor. Significant amounts of 3Z-hexenol (up to 3.54 g kg⁻¹ of olive leaves) were produced and extracted at a yield of 47.7% and with high purity when permeabilized yeast cells were used.