Controlling sol-gel properties enhancing entrapped membrane protein activity through doping additives

Chlorophyllase, a membrane protein, was entrapped in tetramethoxysilane (TMOS)—derived sol-gel and activity examined through a modification of sol-gel properties with doping additives. Polyvinyl alcohol or polyethyleneglycol as uncharged polymeric additives reduced the activity of entrapped chlorophyllase by 60 and 70% respectively, explained by restricted accessibility of chlorophyllase, as revealed by nitrogen desorption experiments. Entrapped chlorophyllase demonstrated 10% activity yield in polyethylenimine-doped gel relative to a polyethylenimine-free control, explained by electrostatic interaction between positively charged polyethylenimine and negatively charged chlorophyllase, considering that polyethylenimine led to a gel with a slightly reduced specific surface area and pore volume, but 20% larger pore size. When chlorophyllase was introduced into sol-gel together with various amounts of glycerol, it demonstrated only slightly lower activity in those gels, even though sol-gel demonstrated decreased specific surface area and pore volume with increasing amount of glycerol. Lipase, as additive, reduced activity of entrapped chlorophyllase, explained by its effect on gel formation, and thus gelation time and gel properties, whereas activity of sol-gel entrapped chlorophyllase associated with monogalactosyl diglyceride (MGDG), was increased by 40%. This study provides an in-depth understanding of the change in sol-gel properties as affected by a wide variety of additives, and the consequent affect on the activity of the membrane protein chlorophyllase.