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Item Quality and safety of sterculia murex, a scientifically unknown nut from Southern Africa.(Elsevier B.V., 2016-11-27) Regnier, T.; Kazaz, S.; Du Plessis, B.; De Jager, K.; Augustyn, W.; Roux-Van der Merwe, R.; Badenhorst, J.Sterculia murex, the wild Lowveld chestnut, is an indigenous tree from southern Africa. In South Africa, this tree has a very restricted distribution in eastern Mpumalanga. The tree is identified by its distinctive flowers and spiky fruits and is also known for its oily and sweet-tasting seeds. Although the seeds are consumed by local communities, no data is available on the safety and commercial value of the nuts. This paper is the first published report on the safety and composition of S. murex nuts since the unpublished report by Wehmeyer in 1986. The microbiological analysis confirms the minimal presence of microorganisms in the raw material, but no contamination or mycotoxins were observed after roasting. Due to the high-water content (9.99%), a drying of ten days at 35 °C was found to be required in order to obtain a suitable product for roasting. The nuts were found to contain 14% protein, with a high percentage of glutamic acid, aspartic acid, arginine, leucine and glycine, and 16% oil. The roasted nuts possess phenolics with a good antioxidant activity and can be considered as a fairly good source of selenium, copper, calcium and iron. The sensory evaluation highlights the aftertaste of the roasted nuts. Therefore, the roasted nuts are best incorporated as an ingredient into breakfast cereals mixes or snacks and energy bars to take advantage of its good nutritive food value.Item Potential of marula (Sclerocarya birrea subsp. caffra) waste for the production of vinegar through surface and submerged fermentation.(Academy of Science of South Africa (ASSAf), 2018-11-27) Molelekoa, Tumisi B.J.; y Regnier, Thierry; Da Silva, Laura S.; Augustyn, Wilma A.Although there is an abundance of indigenous fruits in South Africa, knowledge of their potential uses is mainly restricted to within communities. In this study, marula fruit-processing waste by-products (fruit pulp residue and skin) were used as substrates in surface culture and submerged fermentation methods to produce vinegar (acetic acid) using spontaneous and starter culture techniques. The study revealed the possibility of producing vinegar through both methods of fermentation, with yields of acetic acid ranging between 41 000 mg/L and 57 000 mg/L (surface culture method) and between 41 000 and 54 000 mg/L (submerged culture method). Furthermore, the physicochemical property analyses revealed marula vinegar to be a potential source of bioactive compounds (total phenolics 0.289–0.356 mg/L GAE and total flavonoids 0.146–0.153 mg/L CAE) which displayed a potent antiradical activity against DPPH•: 78.85% for surface culture and 73.03% submerged culture, respectively. The sensory panel recommended application of the vinegar in products such as salad dressing and mayonnaise. Finally, we have demonstrated that the surface culture method using the inoculation technique is more suitable for the production of high-quality vinegar, with possible consideration for commercialisation. Significance: • Marula fruit has high economic importance for South Africa, particularly for the Limpopo Province. • Marula waste can be a source of bioactive compounds, yet comparatively little is reported on the potential use of the waste to produce vinegar. • Self-development of communities through viable and easy to produce commodities from marula fruit needs to be implemented and prioritised in the Limpopo Province.Item Production of pigments by filamentous fungi cultured on agro-industrial by-products using submerged and solid-state fermentation methods.(MDPI, 2021-12-02) Molelekoa, Tumisi Beiri Jeremiah; Regnier, Thierry; Da Silva, Laura Suzanne; Augustyn, Wilma A.The food and pharmaceutical industries are searching for natural colour alternatives as required by consumers. Over the last decades, fungi have emerged as producers of natural pigments. In this paper, five filamentous fungi; Penicillium multicolour, P. canescens, P. herquie, Talaromyces verruculosus and Fusarium solani isolated from soil and producing orange, green, yellow, red and brown pigments, respectively, when cultured on a mixture of green waste and whey were tested. The culture media with varying pH (4.0, 7.0 and 9.0) were incubated at 25 C for 14 days under submerged and solid-state fermentation conditions. Optimal conditions for pigment production were recorded at pH 7.0 and 9.0 while lower biomass and pigment intensities were observed at pH 4.0. The mycelial biomass and pigment intensities were significantly higher for solid-state fermentation (0.06–2.50 g/L and 3.78–4.00 AU) compared to submerged fermentation (0.220–0.470 g/L and 0.295–3.466 AU). The pigment intensities were corroborated by lower L* values with increasing pH. The max values for the pigments were all in the UV region. Finally, this study demonstrated the feasibility of pigment production using green waste: whey cocktails (3:2). For higher biomass and intense pigment production, solid-state fermentation may be a possible strategy for scaling up in manufacturing industries.Item Chemical characterization and toxicity evaluation of fungal pigments for potential application in food, phamarceutical and agricultural industries(Elsevier B.V., 2023-03-31) Molelekoa, Tumisi Beiri Jeremiah; Augustyn, Wilma; Regnier, Thierry; Da Silva, Laura SuzanneConcerns associated with the use of synthetic colourants backs the demand for natural colourants. Thus, the current study aimed at characterizing crude fungal pigments produced by Penicillium multicolour, P. canescens, Talaromyces verruculosus, Fusarium solani and P. herquie. This included their antioxidant and antimicrobial properties together with acute toxicity evaluation on zebrafish embryos. The identification of pigment compounds was achieved through MS and IR data. The study demonstrated a substantial radical scavenging activity of extracts ranging from 65.49 to 74.46%, close to that of ascorbic acid (89.21%). Penicillium canescens and F. solani exhibited a strong antimicrobial activity against Escherichia coli and Enterococcus aerogenes and Salmonella typhi, Staphylococcus aureus and Bacillus cereus at MIC values ranging from 1.5 to 2.5 mg/mL. However, some levels of toxicity were observed for all extracts at a concentration range of 3–5 mg/mL. Pigment by P. multicolour, T. verruculosus and F. solani were tentatively identified through IR and MS data as sclerotiorin (yellow), rubropunctamine (red) and bostrycoidin (red). In conclusion, the study demonstrates a market potential of filamentous fungi pigments due to their antioxidant, antimicrobial activities, and prominent colours. Although there are some toxicity concerns, further tests must be done using molecular docking, albino mice and cell linings.Item Application and stability of fungal pigments using jelly sweets as a food model system.(Wiley, 2023-07-08) Molelekoa, Tumisi Beiri Jeremiah; Da Silva, Laura Suzanne; Regnier, Thierry; Augustyn, WilmaNatural pigments have seen an increase in usage over the past decades due to their acclaimed safety and active biological properties. This is in line with the shift in consumer market preferences requiring a source replacement for synthetic colourants. Filamentous fungi are amongst the natural sources currently explored for pigment production. In this study, the heat, pH and UV light stability of fungal pigments produced by Penicillium multicolour (dark brown), P. canescens (green) and P. herquie (yellow). Talaromyces verruculosus (red) and Fusarium solani (orange) were evaluated. The antioxidant properties of the pigments as influenced by these conditions were ascertained using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The pigments were also applied in a jelly sweet formulation and incubated at ambient temperature for 4 weeks. It was demonstrated that the pigment extracts of P. multicolour and T. verruculosus were significantly affected by higher pH (7.0 and 9.0), where the decline in antioxidant activity was observed. As far as high temperature and UV light exposure are concerned, all the pigment extracts, with exception of P. herquie, maintained an antioxidant activity above 35%. On the other hand, the L*a*b* values showed no overall significant change for heat and UV light exposure with the exception of P. canescens across the four pH levels (3.0, 4.0, 7.0 and 9.0), where an increase in the -a (green index) coupled with a decline in brightness (L* index) and b* (blue index) was observed. Finally, there was no significant change in colour over the 4 weeks of incubation. In conclusion, fungal pigments are generally stable at normal storage conditions (ambient temperature and normal light) and can be suitably applied in jelly sweets.Item Screening for volatile -unsaturated ester-producing yeasts from the feces of wild animals in South Africa.(MDPI, 2022-11-30) Tan, Mélissa; Caro, Yanis; Lebeau, Juliana; Shum-Cheong-Sing, Alain; François, Jean Marie; Regnier, Thierry; Petit, ThomasUnsaturated esters are fruity-aromatic compounds which are largely spread in the volatilome of many different fruits, but they are rarely found in the volatilome of yeasts. The yeast S. suaveolens has been recently shown to produce relatively high amounts of -unsaturated esters and it appears to be an interesting model for the production of these compounds. This study aimed to isolate new-unsaturated ester-producing yeasts by focusing on strains displaying a similar metabolism to S. suaveolens. While the production of -unsaturated esters by S. suaveolens is believed to be closely related to its ability to grow on media containing branched-chain amino acids (isoleucine, leucine and valine) as the sole carbon source (ILV+ phenotype), in this study, an original screening method was developed that selects for yeast strains displaying ILV+ phenotypes and is able to produce -unsaturated esters. Among the 119 yeast strains isolated from the feces of 42 different South African wild animal species, 43 isolates showed the ILV+ phenotype, among which 12 strains were able to produce -unsaturated esters. Two interesting - unsaturated esters were detected in two freshly isolated strains, both identified as Galactomyces candidus. These new esters were detected neither in the volatilome of the reference strain S. suaveolens, nor in any other yeast species previously studied for their aroma production. This work demonstrated the efficiency of an original method to rapidly screen for -unsaturated ester-producing yeasts. In addition, it demonstrated that wild animal feces are interesting resources to isolate novel strains producing compounds with original aromas.