Stability of enzymes and proteins in dried glassy systems: effect of sunlight simulated conditions

LUIS ESPINOSA; CAROLINA SCHEBOR; NORMA SBARBATI DE NUDELMAN; JORGE CHIRIFE

BIOTECHNOLOGY PROGRESS

Wiley InterScience

Año: 2004 vol. 20 p. 1220 - 1224

8756-7938

The purpose of the present work was to study the effects of simulated sunlightconditions on enzyme inactivation and structural damage in dehydrated glassysystems. Freeze-dried samples containing different enzymes (lactase, invertase,lysozyme and amyloglucosidase) were exposed to light using a medium-pressure metalhalide HPA 400 W lamp. After 1 h of light exposure, the samples showed a significantreduction (more than 50%) in the denaturation peak area as analyzed by DSC, andthis could be attributed to protein denaturation. For most of the pure enzymes, theloss of enzymic activity after 1 h of light exposure was around 50%. In the case ofenzymes included in anhydrous model systems (trehalose, raffinose, maltodextrin, anddextran), the remaining activity also decreased dramatically during the light treatment.We showed that the light exposure in dehydrated systems generated both the loss ofenzymic activity and structural changes such as denaturation (observed by DSC) andprotein fragmentation and aggregation (observed by electrophoresis). Overall, we canconclude that a short exposure to the light produces dramatic changes in the enzymicactivity in dehydrated systems with or without protective matrices.