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Theses and dissertations (Applied Sciences)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/6

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Subject: search.filters.subject.Cowpea

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    Anticancer and anti-reactive oxygen species activity of bioactive peptides isolated from vigna unguiculata
    (2024-05) Ramsookmohan, Sonaal; Mellem, John Jason; Dwarka, Depika
    Cancer is a major cause of death globally and continues to escalate with current anticancer drugs associated with severe side effects and resistance driving the need for safer alternative therapeutics. Food proteins, from legumes, are a source of bioactive peptides and studies revealed that they are associated with various therapeutic properties. Cowpea (Vigna unguiculata) is an underutilized nutritious legume crop with promising potential due to its documented protein profile. Therefore, this study evaluated the in vitro anticancer effect of V. unguiculata peptides derived from alcalase and flavourzyme. Physicochemical properties such as water and oil absorption capacities, emulsifying properties, sub-unit composition, amino acid composition among others, were also assessed. Peptides were also evaluated for their antioxidant activity using superoxide radical scavenging, 1,1-diphenyl-2-picrylhydrazil (DPPH) and 2,2’-azino-bis (3 ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays as well as for their apoptotic potential using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), reactive oxygen species (ROS) and caspase 3/7 assays on cancerous (Caco-2 and MCF 7) and healthy (C2C12) cell lines. From results obtained it was observed that the foam capacity for the peptides derived from alcalase and flavourzyme were 78.34 and 82.39%, respectively, which was noted to be significantly different. The physicochemical properties determined their potential application in food industries. Glutamic acid was the most abundant amino acid in all samples while methionine was noted to be the least concentrated amino acid in the flour and alcalase derived sample while proline was the least concentrated in the flavourzyme sample. Results from this study suggest that cowpea samples have antioxidant capabilities with enzymatic hydrolysis contributing to a higher capacity compared to that of raw flour flour samples. From the cowpea flour, the peptide sample derived from alcalase demonstrated the highest DPPH free radical scavenging activity (70.88-80.47%), followed by flavourzyme (67.27-75.84%), while the raw flour sample showed the lowest activity (24.28-66.17%). The ABTS scavenging capacity of the alcalase peptide was in the range of 35.26-85.92%. The MTT cytotoxicity assay revealed that the cowpea peptides and camptothecin showed different sensitivities on the MCF-7 cell lines. The IC50 values of flavourzyme peptide, alcalase peptide and camptothecin were 0.07, 0.09 and 0.07 µg/mL respectively. Cell viability of the cowpea peptides and camptothecin (control) on the Caco-2 cells varied with the different concentrations. Alcalase and flavourzyme samples had IC50 values of 0.15 and 0.11 µg/mL respectively. The apoptotic potential of the peptides was further shown by the caspase 3/7 activity. From the results in this study, it can be ascertained that the cowpea peptides have potential as an anticancer therapeutic agent. Further research is necessary to determine mechanism of action and to conduct in vivo evaluations of these peptides using animal models
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    Valorisation of bambara and cowpea haulms for bioethanol production
    (2020) Okuofu, Somiame Itseme; Pillai, Santhosh Kumar Kuttan
    Bambara and cowpea are important pulses grown in semi-arid South Africa due to their balanced nutrient profile and drought resilient capacity. The haulm is the lignocellulosic residue obtained after grain harvest and are rich in carbohydrates. However, these haulms are underutilised and under researched. The aim of the study, therefore, was to investigate the potential to valorise bambara haulms (BGH) and cowpea haulms (CH) to bioethanol which is the most promising biofuel with commercial prospects currently. The structural and chemical composition of BGH and CH was elucidated using techniques such as compositional analysis, XRD, FTIR, ICP-AES, and SEM. Results indicated a volatile matter and fixed carbon mass fraction of 77.70% and 13.15% (w/w) in BGH and 76.16% and 16.26% (w/w) in CH respectively. The polysaccharides make up the largest fraction (51%), followed by extractives (> 20%), while the lignin in BGH (12%) and CH (10%) was low. X-ray diffraction pattern showed a higher percentage of amorphous regions in BGH (78%) than CH (56%). CH was then subjected to dilute acid pretreatment (DAP) to enhance biosugar production for bioethanol fermentation. The effects of operational factors for DAP including temperature, time, and acid concentration on sugar yield and inhibitor formation was investigated and optimised using response surface methodology (RSM). The solid recovered after DAP was subjected to prehydrolysis with simultaneous saccharification and fermentation (PSSF). In addition, the pretreatment hydrolysate was detoxified and fermented to ethanol using cocultures of Saccharomyces cerevisiae BY4743 and Scheffersomyces stipitis wild type (PsY633). A total ethanol titre of 15.67 g/L was obtained corresponding to 75% conversion efficiency. On the other hand, BGH was subjected to deep eutectic solvent (DES) pretreatment. Five deep eutectic solvents were prepared and screened for their effectiveness in improving enzymatic sugar yield. This was achieved by pretreating BGH with each DES followed by a 48 h enzymatic saccharification. Choline chloride – lactic acid (ChCl-LA) treatment provided the most promising result and was further optimised by investigating the effect of different temperatures and time on cellulose loss and enzymatic sugar yield. ChCl-LA pretreatment at 100°C for 1 h was observed to be the best condition for maximum sugar recovery. The hydrolysate thus obtained was concentrated and fermented for 72 h with S. cerevisiae BY4743. A maximum ethanol yield of 11.57 g/L was obtained. From the results, it is evident that bambara and cowpea haulm are promising substrates for bioethanol production. Dilute acid hydrolysis was shown to be effective in the pretreatment of CH with over 85% of the theoretical sugar recoverable for conversion to bioethanol. In addition, deep eutectic solvents are effective media for breaking the recalcitrance in BGH to achieve high sugar yield for conversion to bioethanol. However, further studies are required to reduce cellulose loss during pretreatment to improve bioethanol yield.