Induction of ferulic acid esterase and xylanase activities in Streptomyces avermitilis UAH30

Ferulic acid esterase activity (FAE) was detected, along with xylanase activity, in culture supernatants from Streptomyces avermitilis UAH30 grown in the presence of the lignocellulosic substrates, oat spelt xylan, wheat bran without starch and sugar cane bagasse. The maximum activity was detected with wheat bran (1.75 mU ml⁻¹). No correlation between FAE activity and the amount of esterified ferulic acid present in the substrate was observed. The addition of either glucose, mannitol or glycerol to the culture medium containing oat spelt xylan resulted in a reduction of 40–75% in the xylanase activity detected in culture supernatants. FAE activity could only be detected in supernatants from cultures grown in the presence of glycerol and mannitol, when commercially available xylanases were added to the assay. These results highlight the importance of assaying for FAE activity in the presence of high levels of xylanase activity.