Role of Feed Forward Neural Networks Coupled with Genetic Algorithm in Capitalizing of Intracellular Alpha-Galactosidase Production by Acinetobacter sp.

Alpha-galactosidase production in submerged fermentation by Acinetobacter sp. was optimized using feed forward neural networks and genetic algorithm (FFNN-GA). Six different parameters, pH, temperature, agitation speed, carbon source (raffinose), nitrogen source (tryptone), and K2HPO4, were chosen and used to construct 6-10-1 topology of feed forward neural network to study interactions between fermentation parameters and enzyme yield. The predicted values were further optimized by genetic algorithm (GA). The predictability of neural networks was further analysed by using mean squared error (MSE), root mean squared error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and R2-value for training and testing data. Using hybrid neural networks and genetic algorithm, alpha-galactosidase production was improved from 7.5 U/mL to 10.2 U/mL

Constitutive Optimized Production of Streptokinase in Saccharomyces cerevisiae Utilizing Glyceraldehyde 3-Phosphate Dehydrogenase Promoter of Pichia pastoris

A novel expression vector constructed from genes of Pichia pastoris was applied for heterologous gene expression in Saccharomyces cerevisiae. Recombinant streptokinase (SK) was synthesized by cloning the region encoding mature SK under the control of glyceraldehyde 3-phosphate dehydrogenase (GAP) promoter of Pichia pastoris in Saccharomyces cerevisiae. SK was intracellularly expressed constitutively, as evidenced by lyticase-nitroanilide and caseinolytic assays. The functional activity was confirmed by plasminogen activation assay and in vitro clot lysis assay. Stability and absence of toxicity to the host with the recombinant expression vector as evidenced by southern analysis and growth profile indicate the application of this expression system for large-scale production of SK. Two-stage statistical approach, Plackett-Burman (PB) design and response surface methodology (RSM) was used for SK production medium optimization. In the first stage, carbon and organic nitrogen sources were qualitatively screened by PB design and in the second stage there was quantitative optimization of four process variables, yeast extract, dextrose, pH, and temperature, by RSM. PB design resulted in dextrose and peptone as best carbon and nitrogen sources for SK production. RSM method, proved as an efficient technique for optimizing process conditions which resulted in 110% increase in SK production, 2352 IU/mL, than for unoptimized conditions

Characterization of sodium cellulose sulphate/poly-dimethyl-diallyl-ammonium chloride biological capsules for immobilized cultivation of microalgae

China Scholarship CouncilBACKGROUND: Microalgae continue to be a focus of industrial bioprocess sustainability practice owing to the numerous biofuels and bioproducts that can be obtained with simultaneous environmental bioremediation applications. However, the extremely dilute nature of large volume microalgal cultures and the small particle size of single-cell microalgae present technological and economic problems of effective dewatering, thus affecting the application of microalgae in process industries. Microalgae immobilization using biocompatible polymeric systems has proved to be an effective strategy to circumvent the heavy dewatering requirement, as this approach provides physical separation between the solid microalgal cells and the liquid medium. RESULTS: In this work, a novel microalgae immobilization carrier, sodium cellulose sulphate/poly-dimethyl-diallyl-ammonium chloride (NaCS-PDMDAAC) capsule, was synthesized and the resulting polymeric capsules were characterized using physicochemical techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX) and nuclear magnetic resonance spectroscopy (NMR). Experimental results showed that the unique properties of NaCS-PDMDAAC capsules, such as pore size, capsule size, mechanical strength, and structural and compositional homogeneity, relevant to microalgae cultivation with batch or continuous nutrient removal can be accurately controlled. CONCLUSION: These polymeric capsules find applications not only with microalgae cultivation but also for other microorganisms. (c) 2012 Society of Chemical Industr

NaCS-PDMDAAC immobilized autotrophic cultivation of Chlorella sp. for wastewater nitrogen and phosphate removal

The unicellular green microalgae, Chlorella sp., entrapped in sodium cellulose sulphate/poly-dimethyl-diallyl-ammonium chloride (NaCS-PDMDAAC) to create microalgae capsules were used to remove total nitrogen (T-N) and phosphate (PO 4 3--P) from artificial wastewater. Batch and semi-continuous cultivations with capsules recycling were carried out in shake flasks within an illuminated incubator. Experimental results showed that the NaCS-PDMDAAC capsules have desirable biophysical properties such as good mechanical stability, biocompatibility with the microalgae cells resulting in biomass enrichment within the capsules, and high substrate concentration tolerance. NaCS-PDMDAAC Chlorella sp. capsules displayed a considerable high T-N and PO 4 3--P removal rate of 12.56 and 10.24mg/g biomass per day respectively. The developed immobilized microalgae system has the potential for continuous wastewater treatment operation with reduced downstream operation cost due to the large size of the capsules being 5-6mm