Involved in the fermentation of L-phenylalanine via a Stickland reaction. Catalyzes the reduction of (E)-cinnamate to yield 3-phenylpropionate. 3-phenylpropanoate + NAD(+) = (E)-cinnamate + H(+) + NADH Amino-acid degradation; L-phenylalanine degradation. In the N-terminal section; belongs to the NADH:flavin oxidoreductase/NADH oxidase family.