Conventional techniques to remove Fe impurities in kaolin typically involve high environmental impact and cost. Alternative methods have been focused on the use of bioleaching where Fe in kaolin is reduced with microorganisms. Early results established a noticeable effect of the bacteria on the redox state of Fe, but knowledge gaps persist such as details on the bacterial-kaolin interactions during attachment of bacteria onto kaolin surface, the metabolites produced by bacteria, and changes in Fe(II)/Fe(III) ion equilibria in solution. To bridge these gaps, this study was conducted to determine the detailed physicochemical changes in bacteria and kaolin during bioleaching through surface, structural, and chemical analysis. Bioleaching experiments were conducted for 10 days where each of the three Bacillus sp. was put in contact (at 9 × 108 CFU) with 20 g of kaolin powder using 200 mL of 10 g/L glucose solution. All samples treated with bacteria showed increasing trends in Fe(III) reduction up until day 6 or 8 followed by a slight decrease towards the end of the ten-day period. Examination of scanning electron microscope (SEM) images suggests that bacterial activity damaged the edges of kaolin particles during bioleaching. Ion chromatography (IC) results showed that during bioleaching, Bacillus sp. produced organic acids such as lactic acid, formic acid, malic acid, acetic acid, and succinic acid. EDS analysis of kaolin before and after bioleaching showed Fe removal efficiencies of up to 65.3%. Analyses of color properties of kaolin before and after bioleaching showed an improvement in whiteness index of up to 13.6%. KEY POINTS: • Dissolution of iron oxides by Bacillus species proven with phenanthroline analysis. • Organic acid type and concentration unique to species detected during bioleaching. • Whiteness index of kaolin is improved after bioleaching.
Numerous studies have revealed the presence of oxidative stress in parasitic infections. However, such studies were lacking in the Malaysian population. Previously, we have provided evidence that oxidative stress is elevated in Malaysians infected with intestinal parasites. Stool examinations revealed that about 47.5% of them were infected with the polymorphic protozoa, Blastocystis hominis. However, they were found to have mixed infection with other intestinal parasites.
This study was initiated to determine the mechanism of iron-uptake in Salmonella typhi. When stressed for iron, microorganisms produce siderophores to obtain the necessary nutrient. Generally two types of siderophores exist: the phenolate-type predominantly produced by bacteria and the hydroxamate-type commonly secreted by fungi. Results of this investigation showed that S. typhi produced siderophores of the phenolate-type since culture supernatant of the organism grown under iron-deprivation supported the growth of the phenolate-dependent auxotroph. The culture supernatant when extracted for phenolate siderophores, also supported the growth of the phenolate auxotroph but not the hydroxamate auxotroph. Production of phenolate-type siderophores were further confirmed using biochemical assays. These results showed that S. typhi utilized the high-affinity iron transport system to obtain the necessary iron.
BACKGROUND: Comparisons of oxidative indices and total antioxidant status between end-stage renal disease (ESRD) patients with or without diabetes is scant, especially in the Asian population.
METHOD: The assays were carried out according to known established protocols.
RESULT: The present study showed that ESRD patients with or without non-insulin-dependent diabetes mellitus (NIDDM) did not have any significant differences in antioxidant enzyme activities, advanced glycated end products (AGE), advanced oxidized protein products (AOPP) and ferric reducing ability of plasma (FRAP), indicating that hyperglycemia does not exacerbate oxidative damage in ESRD. The regulation of catalase and glutathione peroxidase is also altered in ESRD. Elevated FRAP was observed in both ESRD groups (with and without NIDDM). The dialysis process did not alter the antioxidant enzyme activities but decreased AGEs and FRAP and increased AOPP levels.
CONCLUSION: Oxidative stress is present in ESRD but this is not significantly exacerbated by hyperglycemia. The contribution of components in the pathology of renal failure towards oxidative stress exceeds that of hyperglycemia.
The decoction of the whole plant of Elephantopus mollis Kunth. is traditionally consumed to treat various free radical-mediated diseases including cancer and diabetes.