The production of alpha-amylase by Bacillus subtilis was investigated under different cultivation conditions on two different solid substrates as the support, i.e. oil palm empty fruit bunch (OPEFB) fibers and rice straw using solid state fermentation (SSF) process. Both solid substrates were first pre-treated using NaOH to remove lignin and silica and to break down the hemicellulose structures. The influences of incubation time, incubation temperature and the additional carbon and nitrogen sources on the production of alpha-amylase by B. subtilis were investigated. After 48 h of incubation, the highest enzyme activities were obtained at 39.9 U/g and 23.5 U/g for rice straw and OPEFB fibers, respectively. The optimum temperature for alpha-amylase production was observed at 45°C for the OPEFB fibers and 55°C for the rice straw. Among the defined carbohydrates, the addition of glucose (0.02 g/g dry substrate) has significantly improved the production of alpha-amylase. Similar effect was observed when yeast extract (0.01 g/g dry substrate) was supplemented as the additional nitrogen source. Rice straw appeared to be the best solid substrate in producing alpha-amylase (276 U/g) in SSF under these optimum cultivation conditions.
A simple procedure involving simultaneous adsorption and fixation was developed to immobilize β-galactosidase (β-Gal) from Aspergillus oryzae on a polysulfone hollow-fiber membrane module for converting lactose to galactooligosaccharides. Polyethylenimine was used as a polyelectrolyte intermediate layer to provide a positively charged character for β-Gal adsorption. β-Gal adsorbed on polyethylenimine layer was then fixed with cross-linking by glutaraldehyde. The concentrations of polyethylenimine, glutaraldehyde, and β-Gal were significant parameters to achieve high activity yield. The optimum concentration of polyethylenimine and glutaraldehyde were determined as 5% (w/v) and 15% (v/v), respectively. The activity yield on the membrane surface increases as the concentration of β-Gal used during adsorption and fixation increased. The highest activity yield obtained was 1.26 IU cm −2 at 5 mg mL −1 of β-Gal concentration. The activity yield is proportionally dependent on the concentration of the β-Gal employed. Moreover, the immobilized β-Gal exhibited higher specific productivity and stable transgalactosylation activity compared with free β-Gal during the lactose-catalyzed conversion reaction.
Arabidopsis thaliana (A. thaliana) is a small weed which is related to the cabbage and mustard family. This flowering plant has been used widely as a model plant in genetics and molecular biology research since it is the first plant the full sequenced genome. Thus, A. thaliana literature provides plentiful information from genomics and transcriptomics point of view. However, there is still a lack of physiological information regarding its cell suspension cultures which can be powerful research tools in Plant Biotechnology and especially in Plant Systems and Synthetic Biology. In this study, cell growth and sugar uptake of A. thaliana Col ecotype grown in the continuous dark condition were modelled using the modified Monod and Michelis-menten equations. The model included sucrose hydrolysis by the cell-wall invertase enzyme into hexoses (glucose and fructose) and consumption of these hexoses at different rates to support cell growth. All kinetic model parameters were obtained from a control experiment where Col cells were grown on 30 gL-1 sucrose as well as other independent experiments where Col cells were supplied with different concentrations and combinations of sugars. The model adequately described and predicted the growth and sugars profile of A. thaliana cells. This model can also be applied for larger scale of growth with extended expressions for oxygen uptake rate, carbon dioxide production rate etc.
In this study, the oil from Calophyllum inophyllum seeds was extracted using ultrasonic-assisted extraction (UAE) technique. Patricelli's model was used to evaluate the kinetics of oil extraction process in which this model describes extraction in two stages namely rapid washing stage followed by slow diffusion stage. The model parameters were calculated using the experimental data. A good agreement was observed between the experimental and simulated oil yield in all experiments (R20.974), indicating that Patricelli's model was adequate to describe the C. inophyllum seeds oil extraction process. In addition, the influence of three extraction parameters, namely ultrasonic power, extraction temperature and liquid to solid (L/S) ratio on oil yield were studied. It was found that the oil yield increased with increasing ultrasonic power, extraction temperature as well as L/S ratio.
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