FCS and ECH dependent production of phenolic aldehyde and melanin pigment from l-tyrosine in Escherichia coli.

In this study, we engineered E. coli cells to express l-tyrosine converting enzymes, including tyrosine ammonia-lyase (TAL), p-coumarate 3-hydroxylase (C3H), feruloyl-CoA synthetase (FCS), and enoyl-CoA hydratase/aldolase (ECH). A catabolic circuit, which consisted of the protocatechualdehyde and p-hydroxybenzaldehyde production pathways, was reconstituted through combinatorial production of discrete enzymes. First, cells expressing FCS and ECH could convert each 5mM of caffeic acid and ferulic acid into protocatechualdehyde (70.5%) and vanillin (96.5%), respectively. Second, TAL and C3H were co-expressed with FCS and ECH. This strain converted l-tyrosine into caffeic acid, which was then converted into protocatechualdehyde. Ascorbic acid was used as an inhibitor of catechol aldehyde-based melanin formation, and the production yields of protocatechualdehyde and p-hydroxybenzaldehyde were 31.0±5.6 and 24.0±4.2mg/L, respectively. Finally, caffeic acid-based melanin formation was observed with higher production rate of 40.9±6.2mg/L/h by co-expressing FCS and ECH in the presence of caffeic acid.