Ellagic acid production by solid-state fermentation (SSF) using pomegranate peels as a substrate: a review

This review describes the bioprocess to produce ellagic acid (EA) from ellagitannins (ETs) obtained from pomegranate peels. Firstly, the ETs are extracted and purified from the pomegranate peel and used as the only carbon source; polyurethane foam was used to support solid-state fermentation (SSF). Ellagic acid was produced from the fungal hydrolysis of the pomegranate ETs; substrate consumption and EA production were monitored by high-performance liquid chromatography, and several enzymatic activities were assayed. The consumption levels of Ets and glycosides were 66 and 40%, respectively, while EA accumulation reached 42.02 mg g^‑1. Different patterns of enzymatic activities were found. Evidence suggests that the ETs hydrolyzing activity is directly associated with EA accumulation, and the hydrolytic enzyme production (tannin-acyl-hydrolase) represents the critical drawback for a suitable increase in the marketable EA production process. The SSF process is simple and easily reproducible to produce EA from pomegranate peels, an agro-industrial waste product.