No abstract

Biosorption is a cost-effective biotechnological innovation for the removal of heavy metals from aqueous solutions. There is widespread research into ways of utilizing agricultural residues to achieve zero waste. Groundnut shells are biodegradable waste available in large quantities. This study investigated the use of groundnut shells for the biosorption of chromium (VI) ions from an aqueous solution. Groundnut shells were cleaned and crushed to make fractions of particle size in the range of 90-1000 µm. The point of zero charge (pHPZC) and the distribution of oxygenated acidic and basic surface functional groups were determined. In batch experiments, the effect of acid pre-treatment, initial metal concentration, biosorbent particle size, biosorbent dosage, and contact time on biosorption was investigated. The biomass was found to have a pHPZC value of 6 and was dominated by acidic groups. The best biosorption activity was observed at 20 mg/L initial metal concentration and a biosorbent dosage of 10%. The effect of contact time was dependent on the initial chromium (VI) concentration. At 20 mg/L initial chromium (VI) concentration, the biosorption process reached equilibrium within 60 minutes whilst at high (>80 mg) chromium (VI) concentration equilibrium was not reached, even after 240 minutes. The best biosorption activity was observed with acid-treated biomass of particle size 300 µm. The adsorption fitted best with the Langmuir isotherm model and the pseudo-second-order kinetic model (R2 > 0.9982). Groundnut shell biomass has the potential for the removal of chromium (VI) ions from aqueous solutions and possibly from chromium-polluted effluents on an industrial scale.

Studies on the effects of mutations within flavonoid pathway genes on the resultant flavonoid profiles in sorghum are important in the identification and characterisation of varieties with nutritionally superior flavonoid profiles. In this study, we aimed at determining the effect of mutations at one important flavonoid pathway locus, the anthocyanidin synthase (ANS) gene, on grain flavonoid profile in sorghum. Sequence polymorphisms at this locus were determined in sorghum varieties with different seed proanthocyanidin profiles. The proanthocyanidin profiles of 61 local landraces were determined by the DMACA stain and butanol-HCl assay. The Anthocyanidin synthase (ANS) gene was then amplified using PCR from a subset of 11 landraces, and the amplicons subjected to sequence polymorphism analysis using the restriction fragment length polymorphism (RFLP) technique. Results show that 89% of the brown landraces, 4% of the red and none of the white landraces had detectable proanthocyanidins in their grain. Grain proanthocyanidins ranged from 0.1 to 1.8 AU at 550 nm per gram of sample. Using the PCR-RFLP technique, no sequence variations were detected at the ANS locus. Consequently, the different proanthocyanidin profiles observed could not be attributed, according to the methods used, to events at the ANS gene locus. These could be due to mutations at other loci or a combination of genetic and environmental factors.