Biotransformations of cinnamic and ferulic acid with actinomycetes

Biotransformations of cinnamic and ferulic acid catalysed by actinomycetes have been studied. A primary screening was carried out using 535 actinomycetes isolated from soil and able to grow in the presence of cinnamic (500) or ferulic acid (35). A mininiaturized procedure of biotransformation in solid medium showed that, among the strains able to metabolise the substrates, the more frequent behaviours were the degradation of cinnamic acid (often via benzoic acid formation) or transformation in cinnamamide (22 strains), while ferulic acid was mostly degraded with transient accumulation of vanillic acid in few cases. A more restricted screening (57 representative strains) was carried out in submerged cultures: strain GE 107678, identified as Streptomyces halstedii, converted cinnamic acid in cinnamamide (95% molar conversion from 2 g/l of substrate) and ferulic acid in vanillic acid (80% molar conversion from 1 g/l of substrate) with transient formation of low amounts of vanillin (0.10–0.15 g/l).