Research Publications (Applied Sciences)
Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/213
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Item Microbial production of phytases for combating environmental phosphate pollution and other diverse applications(Taylor and Fancis Online, 2016) Kumar, Ashwani; Chanderman, Ashira; Makolomakwa, Melvin; Perumal, Kugen; Singh, SurenConcerns of phosphorus pollution and its impact on environments have driven the biotechnological development of phytases. Phosphoric acid, inositol phosphate, or inositols are produced after hydrolysis of phosphate from phytate, initiated by phytase. Research over the last two decades on microbial phytases has deepened our understanding of their production, optimization, and characterization. Despite the wide availability of phytase producing microorganisms, only a few have been commercially exploited. The current high cost of phytases, inability to withstand high temperatures (>85 C), a limited pH range, and poor storage stability are a major bottleneck in the commercialization of phytases. The development of novel phytases with optimal properties for various applications is a major research challenge. In this paper, recent advances in microbial phytase production, application of tools to optimize higher enzyme production, and characterization of phytases along with potential biotechnological applications are reviewed. Additionally the development of phytase assay methods and functions of phytate and phytate degradation products are discussed.Item Improvement of d-lactate productivity in recombinant Escherichia coli by coupling production with growth(Springer Netherlands, 2012-06) Zhou, Li; Tian, Kang-Ming; Niu, Dan-Dan; Shen, Wei; Shi, Fui-Yang; Singh, Suren; Wang, Zheng-XiangCoupling lactate fermentation with cell growth was investigated in shake-flask and bioreactor cultivation systems by increasing aeration to improve lactate productivity in Escherichia coli CICIM B0013-070 (ackA pta pps pflB dld poxB adhE frdA). In shake-flasks, cells reached 1 g dry wt/l then, cultivated at 100 rpm and 42°C, achieved a twofold higher productivity of lactic acid compared to aerobic and O2-limited two-phase fermentation. The cells in the bioreactor yielded an overall volumetric productivity of 5.5 g/l h and a yield of 86 g lactic acid/100 g glucose which were 66% higher and the same level compared to that of the aerobic and O2-limited two-phase fermentation, respectively, using scaled-up conditions optimized from shake-flask experiments. These results have revealed an approach for improving production of fermentative products in E. coli.Item Improvement of ethanol production from sugarcane molasses through enhanced nutrient supplementation using Saccharomyces cerevisiae(Academic Journals, 2012-03) Nofemele, Zuko; Shukla, Pratyoosh; Trussler, Arthur; Permaul, Kugen; Singh, SurenSaccharomyces cerevisiae as a yeast cream was utilized for alcoholic fermentation using sugar cane molasses. In the present study, fermentation was optimized for urea and yeast hydrolysate (YH) dosage and the combined effect was evaluated. Total sugars as inverts (TSAI) composition of molasses were -1 determined by HPLC as 39% (m/v). Urea concentrations of 4, 2 and 3 gl showed optimal ethanol -1 production at 30, 35 and 40°C respectively. A YH concentration of 0.5 gl resulted in an ethanol yield of 8.7% (m/v) with a fermentation efficiency of 85.12%. Under optimized conditions (35°C) significant improvements were noticed with ethanol yield of 7.8% (m/v) and efficiency of 76.3%.