Composição mineral de vinhos orgânicos Sauvignon blanc elaborados a partir de diferentes fases de maturação das uvas no Vale do São Francisco, Brasil.

O objetivo do presente trabalho foi avaliar os minerais presentes em vinhos elaborados a partir de uvas produzidas de cultivo orgânico, da cultivar Sauvignon Blanc, colhidas em diferentes fases de maturação

Composição mineral de vinhos orgânicos Sauvignon blanc elaborados a partir de diferentes fases de maturação das uvas no Vale do São Francisco, Brasil.

O objetivo do presente trabalho foi avaliar os minerais presentes em vinhos elaborados a partir de uvas produzidas de cultivo orgânico, da cultivar Sauvignon Blanc, colhidas em diferentes fases de maturação

Ethanol production from xylose by pichia stipitis NRRL Y-7124 in a stirred tank bioreactor

The ethanol production by Pichia stipitis was evaluated in a stirred tank bioreactor using semidefined medium containing xylose (90.0 g/l) as the main carbon source. Experimental assays were performed according to a 22 full factorial design to evaluate the influence of aeration (0.25 to 0.75 vvm) and agitation (150 to 250 rpm) conditions on ethanol production. In the studied range of values, the agitation increase and aeration decrease favored ethanol production, which was maximum (26.7 g/l) using 250 rpm and 0.25 vvm, conditions that gave a volumetric oxygen transfer coefficient (kLa value) of 4.9 h-1. Under these conditions, the ethanol yield factor, ethanol productivity, and the process efficiency were 0.32 g/g, 0.32 g/l.h, and 63%, respectively. These results are promising and contribute to the development of a suitable process for ethanol production from xylose by Pichia stipitis.The authors gratefully acknowledge Santander, Fapesp, Capes, and CNPq (Brazil)

RELATIONSHIP BETWEEN MORPHOLOGY, RHEOLOGY AND GLUCOAMYLASE PRODUCTION BY Aspergillus awamori IN SUBMERGED CULTURES

The influence of inoculum preparation on Aspergillus awamori morphology, broth rheology and glucoamylase synthesis in submerged cultures was investigated. A series of runs were performed in fermenters, using initial total reducing sugar concentrations of 20 g/L and 80 g/L. The inocula were prepared in a rotary shaker, at 35oC and 200 rev/min, using a spore concentration of 9.2 x 105 spores/mL and varying both cultivation time and medium pH during the spore germination step. Three types of inocula were used: inoculum cultivated for 24 hours at an initial pH of 5.0, and inocula cultivated for 7 hours at both a pH of 2.5 and a pH of 5.5. Regarding glucoamylase production, the inoculum which provided the best results was shaker cultivated for 7 hours at a pH of 2.5. This inoculum produced glucoamylase of about 1,221 U/L in the fermenter, which was between 20% and 30% higher than those obtained using other inocula

CONSTRUCTION AND OPERATION OF AN IMPELLER RHEOMETER FOR ON-LINE RHEOLOGICAL CHARACTERIZATION OF NON-NEWTONIAN FERMENTATION BROTHS

The present work describes the development and operation of a continuous rotational impeller rheometer for on-line rheological measurements in fermentation broths. In an initial step three devices were calibrated, two of them utilizing helical ribbon impellers and the third a six-bladed impeller. The calibration constants obtained were within the range mentioned in the literature, showing consistency with the methodology employed. In the sequence, the system with one of the helical ribbon impellers (HR39) was selected for on-line continuous rheological measurements due to its small dimensions and its wide measurement range. Finally, the performance of the proposed device, in terms of rheological measurements in Aspergillus awamori broths, was compared to that of a commercial bench rheometer. The comparison of on-line and off-line rheological measurements showed a good agreement between both measurement techniques. Furthermore, results suggest that the proposed on-line rheometer features higher sensitivity and easier operation than the commercial rheomete

Production of 2,3-Butanediol from Sucrose by Klebsiella pneumoniae NRRL B199 in Batch and Fed-Batch Reactors

In batch mode, Klebsiella pneumoniae growth and 2,3-butanediol/acetoin formation are increasingly inhibited by initial sucrose concentrations (S0) over 60 g/L. At non inhibitory conditions, a maximum sucrose consumption rate of 1,5 g/L/h was measured. With S0=204 g/L however, this rate decreased to 0.15 g/L/h. K. pneumoniae fermented 204 g/L sucrose to produce 84.3 g/L of a mixture 2,3-butanediol/acetoin with a yield of 0.41 g/g and a productivity of 1.06 g/L/h. Higher oxygen transfer rates improved the overall process rate but the product yield was reduced. Avoiding substrate inhibition, by performing the fermentation in fed-batch mode, a final 2,3-butanediol/acetoin concentration of 80.0 g/L was achieved. In this case, a productivity of 2.63 g/L/h and a product yield of 0.37 g/g were calculated