The antifouling (AF) potential of the serine protease Esperase HPF (subtilisin) was evaluated for the ability to prevent the formation of a four-species bacterial biofilm. The effects of enzyme activity, time and application of the enzyme were tested on the density and the oxidative metabolism of biofilm developed in microtiter wells. Esperase HPF did not inhibit the oxidative metabolism of the bacterial biofilm or planktonic growth, but the enzyme inhibited biofilm formation by its proteolytic activity as inactivated enzyme had no effect. The effective enzyme concentration was determined over a period of 72 h, as by then all the tested concentrations inhibited biofilm formation maximally. The effective concentrations of the enzymes in solution were the same regardless of time of application (ie before or after biofilm formation), but immobilisation of the enzymes caused a lower effective concentration. Esperase HPF is an attractive alternative to the biocidal compounds used in AF coatings today.
When grown in static culture it appears as if Thermomyces lanuginosus has a biphasic secretion of the extracellular starch-degrading activity. This could be due to the presence of at least two different amylases. By ion-exchange chromatography on DEAE-Trisacryl an α-amylase (EC 3.2.1.1) and a glucoamylase (EC 3.2.1.3) were separated and purified from the extracellular protein from 14-day-old static cultures grown on soluble starch. The hydrolysis of soluble starch by the purified glucoamylase resulted in only glucose as the end product, whereas the α-amylase gave maltose as the smallest end product. The molecular weights and isoelectric points of the enzymes were for glucoamylase 70 000 – 76 000 and pH 4.0, and for α-amylase 54 000 – 57 000 and pH 3.4. An α-glucosidase (EC 3.2.1.20) with a molecular weight of 44 000 – 48 000 and an isoelectric point at pH 3.8 was eluted close to the α-amylase fraction on the DEAE-Trisacryl column.
Growth and differentiation of the imperfect fungus Geotrichum candidum were followed in submerged cultures containing a simple synthetic glucose-salt medium. Uptake of glucose, ammonium and oxygen from the medium were measured during the entire growth period. In 0.1% glucose the fungus grows with one exponential growth phase until all the glucose has been consumed. The arthrospores are formed in the stationary phase. In 0.5% glucose the growth curve has two exponential growth phases, one with a doubling time of 1.8 h and a second one with a doubling time of 4.9 h. The second exponential growth phase, which starts when less than 15% of the glucose and less than 30% of the ammonium have been consumed, is shown to be the sporulation phase. During this growth phase the oxygen saturation in the culture remained cons tant at about 50%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.