Continuous Production of Biogenic Magnetite Nanoparticles by the Marine Bacterium Magnetovibrio blakemorei Strain MV-1T with a Nitrous Oxide Injection Strategy.

Magnetotactic bacteria (MTB) produce magnetosomes, which are membrane-embedded magnetic nanoparticles. Despite their technological applicability, the production of magnetite magnetosomes depends on the cultivation of MTB, which results in low yields. Thus, strategies for the large-scale cultivation of MTB need to be improved. Here, we describe a new approach for bioreactor cultivation of Magnetovibrio blakemorei strain MV-1T. Firstly, a fed-batch with a supplementation of iron source and N2O injection in 24-h pulses was established. After 120 h of cultivation, the production of magnetite reached 24.5 mg∙L-1. The maximum productivity (16.8 mg∙L-1∙day-1) was reached between 48 and 72 h. However, the productivity and mean number of magnetosomes per cell decreased after 72 h. Therefore, continuous culture in the chemostat was established. In the continuous process, magnetite production and productivity were 27.1 mg∙L-1 and 22.7 mg∙L-1∙day-1, respectively, at 120 h. This new approach prevented a decrease in magnetite production in comparison to the fed-batch strategy.

Impact of extraction parameters on the recovery of lipolytic activity from fermented babassu cake.

Enzyme extraction from solid matrix is as important step in solid-state fermentation to obtain soluble enzymes for further immobilization and application in biocatalysis. A method for the recovery of a pool of lipases from Penicillium simplicissimum produced by solid-state fermentation was developed. For lipase recovery different extraction solution was used and phosphate buffer containing Tween 80 and NaCl showed the best results, yielding lipase activity of 85.7 U/g and 65.7 U/g, respectively. The parameters with great impacts on enzyme extraction detected by the Plackett-Burman analysis were studied by Central Composite Rotatable experimental designs where a quadratic model was built showing maximum predicted lipase activity (160 U/g) at 25°C, Tween 80 0.5% (w/v), pH 8.0 and extraction solution 7 mL/g, maintaining constant buffer molarity of 0.1 M and 200 rpm. After the optimization process a 2.5 fold increase in lipase activity in the crude extract was obtained, comparing the intial value (64 U/g) with the experimental design (160 U/g), thus improving the overall productivity of the process.

Adding value to a toxic residue from the biodiesel industry: production of two distinct pool of lipases from Penicillium simplicissimum in castor bean waste.

In countries with a strong agricultural base, such as Brazil, the generation of solid residues is very high. In some cases, these wastes present no utility due to their toxic and allergenic compounds, and so are an environmental concern. The castor bean (Ricinus communis) is a promising candidate for biodiesel production. From the biodiesel production process developed in the Petrobras Research Center using castor bean seeds, a toxic and alkaline waste is produced. The use of agroindustrial wastes in solid-state fermentation (SSF) is a very interesting alternative for obtaining enzymes at low cost. Therefore, in this work, castor bean waste was used, without any treatment, as a culture medium for fungal growth and lipase production. The fungus Penicillium simplicissimum was able to grow and produce an enzyme in this waste. In order to maximize the enzyme production, two sequential designs-Plackett-Burman (variable screening) followed by central composite rotatable design (CCRD)-were carried out, attaining a considerable increase in lipase production, reaching an activity of 155.0 U/g after 96 h of fermentation. The use of experimental design strategy was efficient, leading to an increase of 340% in the lipase production. Zymography showed the presence of different lipases in the crude extract. The partial characterization of such extract showed the occurrence of two lipase pools with distinct characteristics of pH and temperature of action: one group with optimal action at pH 6.5 and 45°C and another one at pH 9.0 and 25°C. These results demonstrate how to add value to a toxic and worthless residue through the production of lipases with distinct characteristics. This pool of enzymes, produced through a low cost methodology, can be applied in different areas of biotechnology.

Production of an acidic and thermostable lipase of the mesophilic fungus Penicillium simplicissimum by solid-state fermentation.

The production of a lipase by a wild-type Brazilian strain of Penicillium simplicissimum in solid-state fermentation of babassu cake, an abundant residue of the oil industry, was studied. The enzyme production reached about 90 U/g in 72 h, with a specific activity of 4.5 U/mg of total proteins. The crude lipase showed high activities at 35-60 degrees C and pH 4.0-6.0, with a maximum activity at 50 degrees C and pH 4.0-5.0. Enzyme stability was enhanced at pH 5.0 and 6.0, with a maximum half-life of 5.02 h at 50 degrees C and pH 5.0. Thus, this lipase shows a thermophilic and thermostable behavior, what is not common among lipases from mesophilic filamentous fungi. The crude enzyme catalysed the hydrolysis of triglycerides and p-nitrophenyl esters (C4:0-C18:0), preferably acting on substrates with medium-chain fatty acids. This non-purified lipase in addition to interesting properties showed a reduced production cost making feasible its applicability in many fields.