Exploration of isoxanthohumol bioconversion from spent hops into 8-prenylnaringenin using resting cells of Eubacterium limosum

Abstract

Hops is an almost unique source of the potent phytoestrogen 8-prenylnaringenin (8-PN). As hops contain only low levels of 8-PN, synthesis may be more attractive than extraction. A strain of the Gram-positive Eubacterium limosum was isolated previously for 8-PN production from more abundant precursor isoxanthohumol (IX) from hops. In this study, spent hops, an industrial side stream from the beer industry, was identified as interesting source of IX. Yet, hopderived compounds are well-known antibacterial agents and the traces of a large variety of different compounds in spent hops interfered with growth and IX conversion. Critical factors to finally enable bacterial 8-PN production from spent hops, using a food and feed grade medium, were evaluated in this research. The use of bacterial resting cells and complex medium at a pH of 7.8-8 best fulfilled the requirements for 8-PN production and generated a solid basis for development of an economic process.

Processing Strategies for Extraction and Concentration of Bitter Acids and Polyphenols from Brewing By-Products: A Comprehensive Review

“…They concluded that 8-prenylnaringenin was the most powerful estrogen molecule formed via the chemical isomerization of desmethylxanthohumol. Moens et al [49] produced 8-prenylnaringenin via bioconversion in an enzymatic route from xanthohumol extracted from spent hops. Jerkovic and Collin [60] used spent hops to produce resveratrol-enriched extracts, reaching 7.7 and 0.7 mg/kg trans-piceid and trans-resveratrol via ethanolic solution (50% v/v), respectively.…”

The Pharmacokinetics of Individual Conjugated Xanthohumol Metabolites Show Efficient Glucuronidation and Higher Bioavailability of Micellar than Native Xanthohumol in a Randomized, Double‐Blind, Crossover Trial in Healthy Humans

“…Two compounds that have similar pharmacokinetic profiles have revealed interesting features as their molecular masses (m/z Bacterial transformation of XN has been observed following in vitro digestion of IXN with Eubacterium limosum, which produces 8-PN. [22] Also Eubacterium ramulus is known to hydrogenate specifically the Michael system in many chalcones. [23] While this may appear to suggest that bacteria were involved in the transformation of XN to 533.1672 and 531.1883, as it has the corresponding mass of M-2H in our volunteers, certain observations contradict this.…”

Current strategies for the management of valuable compounds from hops waste for a circular economy

“…The 8-PN was obtained by bioconversion of isoxanthohumol(IX) from BSH using resting cells of Eubacterium limosum . BSH prenylated flavonoids have antimicrobial properties so the bacteria were used at the resting phase, at a pH of 7.8–8, and in a reinforced clostridial medium for proper enzymatic induction and maximal solubility ( Moens et al, 2020 ). Standardized extracts in 6-PN, 8-PN, IX, and XN of spent hops were administered to post-menopausal women and their pharmacokinetics was evaluated.…”