Daniele Misturini Rossi

The optimization of biohydrogen production by bacteria using residual glycerol from biodiesel synthesis

In this research the production of hydrogen by Klebsiella pneumoniae BLb01 using residual glycerol discharged from a biodiesel fuel production plant was investigated. Klebsiella pneumoniae BLb01 was isolated from a bacteria-rich sludge of an upflow anaerobic sludge blanket reactor (UASB) of a soybean processing plant. A Plackett–Burman design (P-B) and Response Surface Methodology (RSM) were employed to determine the optimal condition for enhanced hydrogen production. The maximal hydrogen production, which was 45.0 mol % and with 98% of glycerol degradation, was achieved with the optimized medium with the following composition: 30 g L−1 glycerol; 3 g L−1 yeast ex tract 3 g L−1 K2HPO4; 1 g L−1 KH2PO4; temperature 39°C and pH 9.0. These results show the ability of this new strain of effectively converting residual glycerol into value-added energy products.

Production of High-protein Hydrolysate from Poultry Industry Residue and their Molecular Profiles

The use of mechanically deboned poultry meat (MDPM) as a source of raw protein for the enzymatic preparation of hydrolysates was investigated using commercial proteases Alcalase and Flavourzyme. Hydrolysis conditions were optimized by response surface methodology, and the influence of temperature, pH, and enzyme concentration were evaluated to determine the hydrolysis index. For Alcalase, optimal values of temperature, pH, and enzyme concentration were found to be 50°C, 7.5%, and 2.5%, respectively, while for Flavourzyme the optimized variables were at 50°C, 6.0%, and 3.5%, respectively. Compared to raw MDPM, Alcalase produced a very high recovery of 89% of the nitrogen from the hydrolysates, while for Flavourzyme recovery was around 67%. Alcalase was used to produce a spray-dried hydrolysate containing 62% of total protein with molecular weights ranging from 5,807 to 12,000 Da, and had excellent microbiological quality.

Comparative production of xylanase and the liberation of xylooligosaccharides from lignocellulosic biomass by Aspergillus brasiliensis BLf1 and recombinant Aspergillus nidulans XynC A773

We investigated the simultaneous production of xylanase and the liberation of xylooligosaccharides in rice husk solid-state cultivations of Aspergillus brasiliensis BLf1 and by the recombinant Aspergillus nidulans XynC A773 strain. The bioprocess was optimised by experimental fractional design and response surface analysis. Results show that both fungi strains produced xylanases and their activities were dependent on the addition of basal medium, moisture content and the interactions between particle size and inoculum size, producing maximum xylanase activities of 230.7 U g 1 substrate for A. brasiliensis, and 187.9 U g 1 substrate for A. nidulans XynC. Xylooligosaccharides were liberated in the same cultures, with concentrations up to 17.6 mg g 1 and 23.9 mg g 1 of substrate for A. brasiliensis and A. nidulans XynC, respectively, both strains presenting similar profiles, with xylose residues varying from X3 to X6. These results suggest the possibility of lowering production costs of enzymes for food applications and oligosaccharides.