Growth and release of hydroxycinnamic acids from Brewer’s spent grain by Streptomyces avermitilis CECT 3339

Streptomyces avermitilis CECT 3339 is grown on Brewer’s spent grain (BSG) and the production of feruloyl esterase (FAE) and (1→4)-β-d-xylan xilanohydrolase (xylanase) activities is studied over 5 days. Maximum level of xylanases was found at day 1. FAE activity on methyl ferulate reached a maximum level at day 2, whereas FAE activity on feruloylated oligosaccharides, either from wheat bran or sugar-beet pulp, was maximal at day 1. The cultures (1–5 days) from S. avermilitis CECT 3339 grown on BSG and on other two agro-industrial residues such as de-starched wheat bran and sugar-beet pulp were tested for the release of hydroxycinnamic acids (ferulic and p-coumaric acids) from BSG. Most ferulic acid (FA) was released when culture supernatants from day 1 and BSG as carbon source (43% of total alkali-extractable ferulic acid) and from day 2 and de-starched wheat bran as carbon source (41.2%) were used. The level of p-coumaric released in all cases was lower (<9% of total alkali-extractable p-coumaric acid; pCA). The importance of the time of growth for the enzyme production involved in the hydrolysis of BSG is discussed.