Marilize Le Roes-Hill | CPUT (original) (raw)

Papers by Marilize Le Roes-Hill

Water, Oct 13, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

International Journal of Biological Macromolecules, Mar 1, 2018

This work reports for the first time the secretory expression of the small laccase (SLAC) from St... more This work reports for the first time the secretory expression of the small laccase (SLAC) from Streptomyces coelicolor A3(2) in Pichia pastoris. Using an AOX1 promoter and α factor as a secretion signal, the recombinant P. pastoris harbouring the laccase gene (rSLAC) produced high titres of extracellular laccase (500 ± 10 U/l), which were further increased seven fold by pre-incubation at 80 °C for 30 min. The enzyme (∼38 kDa) had an optimum activity at 80 °C, but optimum pH varied with substrate used. Km values for ABTS, SGZ and 2,6-DMP were 142.85 μM, 10 μM and 54.55 μM and the corresponding kcat values were 60.6 s-1, 25.36 s-1 and 27.84 s-1, respectively. The t1/2 values of the rSLAC at 60 °C, 70 °C, 80 °C were 60 h, 32 h and 10 h, respectively. The enzyme deactivation energy (Ed) was 117.275 kJ/mol while ΔG, ΔH and ΔS for thermal inactivation of the rSLAC were all positive. The rSLAC decolourised more than 90% of Brilliant Blue G and Trypan Blue dye in 6 h without the addition of a mediator. High titres of SLAC expressed in P. pastoris enhance its potential for various industrial applications.

Trends in Biotechnology, Apr 1, 2009

Process Biochemistry, Oct 1, 2022

Genome Announcements, Oct 5, 2017

We report here the draft genome sequence of the soil bacterium Gordonia lacunae BS2 T (ϭ DSM 4508... more We report here the draft genome sequence of the soil bacterium Gordonia lacunae BS2 T (ϭ DSM 45085 T ϭ JCM 14873 T ϭ NRRL B-24551 T), isolated from an estuary in Plettenberg Bay, South Africa. Analysis of the draft genome revealed that more than 40% of the secondary metabolite biosynthetic genes encode new compounds.

Proteins, Sep 9, 2020

Expansins have the remarkable ability to loosen plant cell walls and cellulose material without s... more Expansins have the remarkable ability to loosen plant cell walls and cellulose material without showing catalytic activity and therefore have potential applications in biomass degradation. To support the study of sequence‐structure‐function relationships and the search for novel expansins, the Expansin Engineering Database (ExED, https://exed.biocatnet.de) collected sequence and structure data on expansins from Bacteria, Fungi, and Viridiplantae, and expansin‐like homologues such as carbohydrate binding modules, glycoside hydrolases, loosenins, swollenins, cerato‐platanins, and EXPNs. Based on global sequence alignment and protein sequence network analysis, the sequences are highly diverse. However, many similarities were found between the expansin domains. Newly created profile hidden Markov models of the two expansin domains enable standard numbering schemes, comprehensive conservation analyses, and genome annotation. Conserved key amino acids in the expansin domains were identified, a refined classification of expansins and carbohydrate binding modules was proposed, and new sequence motifs facilitate the search of novel candidate genes and the engineering of expansins.

FEMS Microbiology Ecology, Dec 11, 2013

In this study, three biological sand filter (BSF) were contaminated with a synthetic iron-[1500 m... more In this study, three biological sand filter (BSF) were contaminated with a synthetic iron-[1500 mg L-1 Fe(II), 500 mg L-1 Fe(III)] and sulphate-rich (6000 mg L-1 SO 2/4-) acid mine drainage (AMD) (pH = 2), for 24 days, to assess the remediation capacity and the evolution of autochthonous bacterial communities (monitored by T-RFLP and 16S rRNA gene clone libraries). To stimulate BSF bioremediation involving sulphate-reducing bacteria, a readily degradable carbon source (glucose, 8000 mg L-1) was incorporated into the influent AMD. Complete neutralization and average removal efficiencies of 81.5 (±5.6)%, 95.8 (±1.2)% and 32.8 (±14.0)% for Fe(II), Fe(III) and sulphate were observed, respectively. Our results suggest that microbial iron reduction and sulphate reduction associated with iron precipitation were the main processes contributing to AMD neutralization. The effect of AMD on BSF sediment bacterial communities was highly reproducible. There was a decrease in diversity, and notably a single dominant operational taxonomic unit (OTU), closely related to Clostridium beijerinckii, which represented up to 65% of the total community at the end of the study period.

Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology, Nov 6, 2017

As part of an antibiotic screening program, an actinobacterium, strain HMC13 T , was isolated fro... more As part of an antibiotic screening program, an actinobacterium, strain HMC13 T , was isolated from soil collected from the banks of the Gamka River, Western Cape Province, South Africa. The isolate was found to produce branched mycelia that differentiated into spiral spore chains with spiny spores. 16S rRNA gene sequence analysis showed the strain to be closely related to Streptomyces caelestis NRRL 2418 T (99.72%) and Streptomyces azureus NBRC 12744 T (99.51%). Chemotaxonomic analyses confirmed the classification of the strain as a member of the genus Streptomyces: LL-DAP in the peptidoglycan, no diagnostic sugars in the whole cell sugar pattern, dominant menaquinones including MK9(H 8), MK9(H 6), and the polar lipids detected included phosphatidylethanolamine. The fatty acid profile revealed the presence of mostly branched, saturated fatty acids: iso-C 15:0 (14.4%), anteiso-C 15:0 (21.1%), iso-C 16:0 (16.8%), C 16:1 x7c/2-OH iso-C 15:0 (5.8%), C 16:0 (6.2%), iso-C 17:1 x9c (5.8%), iso-C 17:0 (5.9%), and anteiso-C 17:0 (9.6%). Strain HMC13 T is a tyrosinase producer and exhibits very strong antibiosis against Mycobacterium aurum A? and Staphylococcus aureus subsp. aureus ATCC 33591 (methicillin resistant), while only weak activity was observed against Bacillus cereus ATCC 10876, Enterococcus faecium VanA (vancomycin resistant), Enterococcus faecalis ATCC 51299 (vancomycin resistant) and Candida tropicalis ATCC 750 T. Strain HMC13 T (= LMG 28849 T = NRRL B-65294 T) is proposed as the type strain of a new species, to be named Streptomyces swartbergensis sp. nov.

International Journal of Systematic and Evolutionary Microbiology, Jun 1, 2009

Process Biochemistry, Dec 1, 2012

2,6-Dimethoxyphenol is a phenolic compound that is extensively used for the measurement of laccas... more 2,6-Dimethoxyphenol is a phenolic compound that is extensively used for the measurement of laccase activity, but is often not exploited for its potential as an antioxidant compound. Since laccase can be used to modify phenolic antioxidants as a way of improving their activities, the present study investigated the laccase-mediated oxidation of 2,6-dimethoxyphenol in biphasic or homogenous aqueous-organic media for the production of compounds with higher antioxidant capacity than the starting substrate. The main product was a dimer (m/z 305.0672), which was further characterized as a symmetrical CC linked 3,3',5,5'-tetramethoxy biphenyl-4,4'-diol. In the monophasic system, the dimer was preferentially formed when acetone was used as cosolvent, while in the biphasic system, formation of the dimer increased as the concentration of ethyl acetate was increased from 50 to 90 %. The dimer showed higher antioxidant capacity than the substrate (≈ 2×) as demonstrated by standard antioxidant assays (DPPH and FRAP). These results demonstrate that a product of the laccase-catalysed oxidation of 2,6-dimethoxyphenol can find useful application as a bioactive compound.

South African Journal of Botany, Mar 1, 2018

polysaccharides, alkaloids, and phenolics were revealed using histochemical staining, which were ... more polysaccharides, alkaloids, and phenolics were revealed using histochemical staining, which were substantiated with preliminary phytochemistry. This study serves as a basis for the identification and description of the secretory apparatus in T. minuta L. and the compounds they produce. Additionally, this study holds the potential to sway the change of the status of T. minuta L. from weed to underutilised minor crop.

Biotechnology and Bioprocess Engineering, Mar 1, 2014

The formation of environmentally toxic acidic waste from mining activities is a worldwide problem... more The formation of environmentally toxic acidic waste from mining activities is a worldwide problem. Neutralization of this waste can be accomplished by physicochemical and/or biological means. In this short-term study, synthetic acid mine drainage was added to sandfilled mesocosms containing silica-dominated (quartz) sand. Glucose was added as a carbon source for microbial iron and/or sulphate reduction. Replicates contained two separate batches of sand obtained from the same quarry site. The investigations used to assess and compare the chemical and biological functioning of the replicates included system hydraulic conductivity measurements, sand chemistry, effluent chemistry and bacterial community fingerprinting. Minor differences in composition of the sand, including the levels of available nutrients and micronutrients, resulted in major differences in measured parameters. 2 Significant differences in effluent chemistry were found in systems containing different batches of sand. It was demonstrated that the characteristics of the sand and the presence of acid mine drainage impacted the bacterial community structure and function. The importance of the physical substrate on the selection of functional microbial communities in systems remediating AMD should not be underestimated. The physical substrate should be carefully selected and it may be prudent to include small-scale comparative studies in each particular setting prior to full-scale implementation.

Scientific Reports, Jul 8, 2021

The distribution of phytochemicals and their contribution to antioxidant potentials in whole and ... more The distribution of phytochemicals and their contribution to antioxidant potentials in whole and dehulled Bambara groundnut (BGN) seeds was evaluated. Whole BGN seeds were sorted using the testa and hilium colour and further grouped into whole and dehulled BGN seeds. Extractions of both whole and dehulled BGN seeds was done using methanol and the extracts assayed for total phenolics (TPC), flavanol, flavonol, anthocyanin content, oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP). Methanolic extract of whole BGN seed exhibited higher flavanol and flavonol content as well as significantly higher in-vitro antioxidant activities than dehulled BGN seeds. The TPC of whole BGN seed extract ranged from 3.6 to 11.0 GAE/g, while that of dehulled BGN ranged from 2.7 to 3.2 GAE/g. Identification of phenolics in whole and dehulled BGN seed extract using UPLC-qTOF-MS, revealed the presence of monoterpenoids (iridoids), phenolic acids, flavonoids and lignans. Bivariate correlations showed anthocyanin demonstrated weak positive correlation between flavanol, flavonol and ORAC for whole BGN seed extract; and negative correlation between flavanol, TPC, FRAP and ORAC for dehulled BGN. Aside the effect of dehulling, whole BGN seeds exhibited the presence of phytochemicals with beneficial properties for food and industrial application. Legumes are crops belonging to the Fabaceae family which due to the enormous protein and fibre available in their seeds, contributes a very significant and healthy portion to the human diet 1. Apart from their nutritive worth, legumes are rich in secondary metabolites 2 known for their contribution to a wide array of biological activities. One such legume is Bambara groundnut (BGN; Vigna subterranea), an underutilized neglected legume, grown for its seeds 3. Major producers of BGN in Africa are Nigeria, Niger, Ghana and Cote d'Ivoire; but widely grown in Eastern Africa and Madagascar 4. Likewise, in South Africa, major areas producing BGN seeds are Limpopo, Mpumalanga and KwaZulu-Natal Provinces. There are various opinions as to the origin of BGN in South Africa because the Vendas claim that they brought the legume to South Africa from Central Africa, while the people of Bolobedu also claim to have brought the seeds when they arrived in the south 5, 6. Nevertheless, the claim by the Vendas is supported by the name 'Nduhu-mvenda' meaning groundnut of Venda land and the traditional ritual, which is often performed during the harvest of BGN in Venda 7. Among the repository of underutilized crops, BGN has significant potential to ensure investment towards its improvement 8. Its seeds possess the ability to mitigate malnutrition and increase food security as they contain about 57-67% of carbohydrate and 15-27% of proteins, although lower concentrations of lipids (< 10%) have been reported 9-12. Bambara groundnut acts as a vital source of protein in the diets of a vast populace in Africa, especially to members of the populace that are unable to pay for animal protein. Besides, BGN is associated with diverse indigenous knowledge among cultures who depend on it for sustenance.

Ecological Engineering, Jun 1, 2018

The flow of effluent through treatment wetlands is influenced by the infrastructure setup , the e... more The flow of effluent through treatment wetlands is influenced by the infrastructure setup , the effluent character, the type of hydraulic flow, the mode of operation, the type of substrate, and the type and quantity of biomass. Current flow models have not been well validated, and/or do not accurately account for biomass clogging. In this study, treatment wetlands containing Dune or River sand with similar particle size distributions exhibited significant disparities in achievable flow rates. To gain insight into this phenomenon, further investigations were conducted to compare: (i) sand particle characteristics (size, elemental and mineral composition, grain morphology), (ii) the relationships between mineral composition and shape of the sand particles, (iii) the hydraulic conductivity of the different sand types before and after inducement of biomass growth, and (iv) the measured hydraulic conductivities with those predicted using the fractional packing Kozeny-Carman model. Using automated scanning electron microscopy (QEMSCAN™) it was determined that the shape of the quartz particles of the River sand (98% quartz) and calcite particles of the Dune sand (81% quartz, 18% calcite) were less round and more angular than the quartz particles of the Dune sand, and that the River sand particles were conglomerate in nature and/or fractured. The hydraulic conductivities of the Dune and River sands were significantly different (0.284 and 0.015 mm s −1 , respectively), and the hydraulic conductivity of the Dune sand decreased by 51% due to biomass accumulation. The fractional packing model overestimated the measured values.

The Journal of Antibiotics, Jun 25, 2014

Two novel members of the genus Amycolatopsis were isolated from soil samples collected in South A... more Two novel members of the genus Amycolatopsis were isolated from soil samples collected in South Africa. Strains JS72 T and M29 T clustered in the same clade in the 16S-rRNA, gyrB-16S-rRNA and gyrB-recN gene trees. Both strains showed anti-mycobacterial activity. The oxyB P450 monooxygenase B gene required for the production of glycopeptide antibiotics was detected in both strains, while strain JS72 T was also shown to contain the 3-amino-5-hydroxy-benzoic acid synthase gene, which is required for the production of the ansamycin class of antibiotics. Genetic distance values (based on the gyrB and recN genes) were calculated between strains JS72 T and M29 T and their closest phylogenetic relatives. The values for strain JS72 T were all above the threshold values of 0.02 and 0.04, respectively, that have been proposed to distinguish Amycolatopsis-type strains. The gyrB-based values for strain M29 T were above the threshold for all but one strain; the recN-based values were all above the threshold. These data, along with DNA-DNA hybridization data, showed that strains JS72 T and M29 T belong to distinct genomic species. The physiological, phylogenetic and genetic distance data support the description of strains JS72 T and M29 T as the type strains of novel species, for which the names Amycolatopsis speibonae sp. nov. (¼ DSM 46660 T ¼ NRRL B-24958 T) and Amycolatopsis roodepoortensis sp. nov. (¼ DSM 46661 T ¼ NRRL B-24959 T) are proposed, respectively.

International Journal of Systematic and Evolutionary Microbiology, Jun 30, 2009

Heliyon, Sep 1, 2018

Bambara groundnut (Vigna subterranea) an indigenous legume proclaimed to have medicinal propertie... more Bambara groundnut (Vigna subterranea) an indigenous legume proclaimed to have medicinal properties within rural areas. Therefore, this study aimed to identify possible medicinal properties of Bambara groundnut (BGN). Flavonoids and tannins were highly concentrated in the red and brown BGN hulls. Among the flavonoid compounds rutin was observed in highest concentrations in brown hull (24.458 AE 0.234 mg g À1) and myricetin (1.800 AE 0.771 mg g À1). While among tannin compounds chlorogenic acid was found in highest concentrations (0.115 AE 0.199 mg g À1) and ellagic acid in red hull (0.105 AE 0.082 mg g À1). The form and colour of the BGN were all important factors to optimize the best extraction yield of phytochemicals. Overall the hulls of the BGN were the optimum source of flavonoids and tannins.