https://commons.ru.ac.za/vital/access/manager/Index en-us 5 https://commons.ru.ac.za/vital/access/manager/Repository/vital:3921 Wed 12 May 2021 18:42:58 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4132 50%). In the current study, the specific activities of a range of extracellular hydrolytic enzymes (L-alanine aminopeptidase, L-leucine aminopeptidase, arylsulphatase, α-glucosidase, β- glucosidase, protease and lipase) were monitored in a sulfide gradient within a biosulphidogenic RSBR. Data obtained indicated that the specific enzymatic activities increased with the depth of the RSBR and also correlated with a number of the physicochemical parameters including sulfide, alkalinity and sulfate. The activities of α- glucosidase and β-glucosidase were higher than that of the other enzymes studied. Lipase activity was relatively low and studies conducted on the enzyme-enzyme interaction using specific enzyme inhibitors indicated that lipases were probably being digested by the proteases. Further studies to determine the impact of sulfide on the enzymes, showed an increase in the enzyme activity with increasing sulfide concentration. Possible direct affects were investigated by looking for changes in the Michaelis constant (Km) and the maximal velocity (Vmax) of the crude enzymes with varying sulfide concentrations (250, 400 and 500 mg/l) using natural and synthetic substrates. The results showed no significant difference in both the Km and the Vmax for any of the hydrolytic enzymes except for the protease. The latter showed a statistically significant increase in the Km with increasing sulfide concentration. Although this indicated a direct interaction, this difference was not large enough to be of biochemical significance and was consequently not solely responsible for the enhanced hydrolysis observed in the RSBR. Investigation into the floc characteristics indicated that the biosulphidogenic RSBR flocs were generally small in size and became more dendritic with the depth of the RSBR. Based on the above data, the previously proposed descriptive models of enhanced hydrolysis of particulate organic matter in a biosulphidogenic RSBR has been revised. It is thought that the effect of sulfide on the hydrolysis step is primarily indirect and that the reduction in floc size and alteration of the floc shape to a more dendritic form is central to the success of the process.]]> Wed 12 May 2021 18:32:30 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4080 Wed 12 May 2021 16:35:29 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4000 Wed 12 May 2021 15:46:37 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:28697 Thu 20 Apr 2023 10:03:31 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:4012 Thu 13 May 2021 03:57:39 SAST ]]> https://commons.ru.ac.za/vital/access/manager/Repository/vital:3961 Thu 13 May 2021 01:02:05 SAST ]]>