BACKGROUNDRecombinant protein excretion has become a mainstream strategy in reducing downstream processing costs. However, recombinant protein excretion is often bottlenecked by cell lysis and plasmid stability. In the present study, recombinant Escherichia coli cell immobilization was performed on a hollow fiber membrane. Tryptone concentration in the expression medium (Super Optimal Broth), which was used as a nitrogen source, was varied between 5 and 20 g L−1 to enhance the excretion of recombinant cyclodextrin glucanotransferase (CGTase), plasmid stability, and resistance of cell lysis.RESULTSThe immobilized cells with 5 g L−1 concentration of tryptone improved the plasmid stability with 119% improvement and 69% reduction of cell lysis without remarkably altering the excretion of CGTase compared with the tryptone concentration of 20 g L−1. The immobilized cells showed a 2‐fold increase in excretion of CGTase, a 45% reduction in cell lysis, and a 172% gain in plasmid stability in comparison with the free cells. Moreover, the doubling time increased to 58 and 5 h for the immobilized and free cells, respectively. The immobilized cells recorded 2301.62 U mL−1 of cumulative CGTase activity through seven fermentation cycles using the untreated membrane, marking their excellent reusability.CONCLUSIONThis new technique of recombinant protein expression utilizing an immobilized cell system under low tryptone concentration is an outstanding approach to improve recombinant CGTase excretion and plasmid stability with low cell lysis. © 2023 Society of Chemical Industry (SCI).
Cell immobilization has been applied in various industries, including chemical manufacturing, food, pharmaceutical, and textile. Recently, innovations in cell immobilization techniques and support materials have been put forward for application in high value-added chemical biosynthesis, such as cyclodextrin (CD). The techniques, support materials, and process parameters of cell immobilization play important roles in achieving high CD yield. This review should help one choose the correct cell immobilization technique and support for a CD biosynthesis setup. Previously, CD biosynthesis utilized free cells, even though they present difficulties such as the low product yield, cell lysis, unstable plasmid, and non-reusable cells. This review highlights how the problems that arise from free-cell bioreactors could be mitigated by cell immobilization. The process conditions of cell immobilization for CD production are also presented.
BACKGROUNDIncorporating fish oils into commonly consumed foods is an emerging technique for increasing the daily intake of omega‐3 fatty acid. However, the high vulnerability of fish oil towards oxidative deterioration reduces shelf life stability. Microencapsulation by spray drying with different combinations of biopolymers and other parameters may provide a solution by preventing further oxidation of fish oil and permitting its delivery to food items. This study emphasised the influence of developed biopolymer materials (maltodextrin, maltodextrin + gum arabic, maltodextrin + starch, maltodextrin + whey protein isolates and maltodextrin + sodium caseinate) for emulsion formulation, inlet air temperature (160, 170, 180, 190 and 200 °C) and emulsion ratios (15, 20, 25, 30 and 35%) on the physicochemical properties of powdered menhaden fish oil by spray drying technique.RESULTSMicroencapsulated menhaden fish oil was evaluated for its moisture content, size distribution, microcapsule efficiency, peroxide value, free fatty acid, acid value and morphological structure. It was observed that the coating materials of maltodextrin + whey protein isolates gave the lowest moisture content and peroxide value of 4.410% and 4.031 mEq kg−1, respectively. The morphological images showed a smooth surface with no cracks and minimal shrinkage, indicating lower permeability to gases and effectively protecting the oil against deterioration.CONCLUSIONThe spray drying procedure using maltodextrin + whey protein isolates at an inlet air temperature 190 °C and emulsion ratio of 30% successfully produced fish oil microcapsules with improved properties. © 2023 Society of Chemical Industry (SCI).
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