The active site of Sporotrichum thermophile type C feruloyl esterase (StFaeC) was probed using a series of C1–C4 alkyl ferulates. The affinities for straight and branched alkyl ferulates were demonstrated by the Km values of 1.64–0.51 and 0.19–0.1, respectively. Comparison of kcat and kcat/Km values shows that the enzyme hydrolyzed n-propyl ferulate faster and iso-propyl ferulate more efficiently. Alkyl ferulates were applied also for substrate selectivity mapping of feruloyl esterase to catalyze feruloyl group transfer to l-arabinose, using as a reaction system a ternary water–organic mixture consisting of n-hexane, t-butanol and water. Lengthening the aliphatic side chain was the most significant factor causing lower synthetic activity of the enzyme. The reaction parameters affecting the feruloylation rate and the conversion of the enzymatic process, such as the temperature and substrate concentration have been investigated. Under identical reaction conditions, the enzyme feruloylated other monosaccharides such as d-arabinose, d-glucose, d-xylose, d-mannose, d-fructose, d-galactose, d-ribose and model substrates such as 4-nitrophenyl α-l-arabinofuranoside and 4-nitrophenyl α-l-arabinopyranoside.