ASPECTS OF THE RESISTANCE OF LACTIC-ACID BACTERIA TO HOP BITTER ACIDS

Resistance to trans-isohumulone is found only in those lactic acid bacteria which can grow in beer. The degree of resistance could not be altered by plasmid curing, or mutation induced by u.v. light. Organisms resistant to trans-isohumulone were resistant to the related hop acids (-)-humulone and colupulone. Equally, organisms sensitive to trans-isohumulone were also sensitive to related compounds. No other features correlated with hop resistance, including cell morphology, colony morphology, pH range for growth, sugar utilization profile, products of metabolism, manganese requirement and sensitivity to superoxide radicals, expression of cellular proteins, and resistance or sensitivity to selected antibacterial agents.