Abstract Studies have shown that the supplementation of vegetable oils, in poly(3-hydroxybutyrate) production, provides an increase in the process productivity, besides inducing lipase activity in the medium. The supplementation with miniemulsified oils could potentialize these results. In this work, the influence of supplementation of the medium with soybean oil, without treatment and miniemulsified, on polymerr production was evaluated. The best moment to supplement the medium and its influence on lipase activity were also analyzed. The results showed that the supplementation with miniemulsified soybean oil promoted an increase of 9.7% in polymer content and the productivity increased from 0.58 to 0.63 g.L-1.h-1, when compared with the culture without supplementation. The best time to add the supplement is in the beginning of the production phase. The lipase activity was higher for the culture supplemented with miniemulsified soybean oil, promoting the use of the oil.

Poly(3-hydroxybutyrate) (P(3HB)) is a carbon and intracellular storage source for different microorganisms and its production can achieve high productivities by means of high cell density cultures. The aim of this study was to propose a high cell density strategy for P(3HB) production by Cupriavidus necator. The exponential growth phase demands an accurate control of the oxygen transfer system in the bioreactor, due to maximum specific growth rate (µXr), and, consequently, a maximum specific oxygen uptake rate (QO2), in addition to significant residual biomass (Xr) growth in high cell density cultures. In this context, this work investigated the strategy for obtaining high cell density, with the inclusion of a linear growth phase for P(3HB) production by C. necator in a fed-batch culture. The linear growth phase was included between the exponential growth phase and the P(3HB) production phase as a strategy to reduce the specific growth rate (µXr) and specific oxygen uptake rate (QO2), with constant residual biomass growth rate (d(V.Xr)/dt = k = constant) and linear increase of biomass. Three strategies of culture were performed. The results showed that a high residual biomass concentration (30 gXr.L-1) can be reached by the inclusion of the linear growth strategy and specific growth rates (µXr) between 0.08 and 0.05 h-1, at the beginning of the production phase, are necessary to attain a high P(3HB) productivity.

Ammonium oxidation was thought to be an exclusively aerobic process; however, as recently described in the literature, it is also possible under anaerobic conditions and this process was named ANAMMOX. This work describes the operation of a system consisting of a denitrifying reactor coupled to a nitrifying reactor used for removal of nitrogen from slaughterhouse wastewater. During operation of the denitrifying reactor an average nitrogen ammonium removal rate of 50 mg/Ld was observed. This biomass was used to seed a second reactor, operated in repeated fed batch mode, fed with synthetic medium specific to the growth of bacteria responsible for the ANAMMOX process. The nitrogen loading rate varied between 33 and 67 mgN/Ld and average nitrogen removal was 95% and 40%, respectively. Results of fluorescence in situ hybridization (FISH) confirmed the presence of anammox-like microorganisms in the enriched biomass.

Cell growth and retamycin production in Streptomyces olindensis So20 were studied at different dissolved oxygen levels during fermentation. The profiles for cell growth and retamycin production in an experiment with dissolved oxygen control at 5% air saturation during production were similar to those in an experiment without dissolved oxygen control. However, despite slower cell growth, a twofold increase in the final retamycin concentration was achieved when dissolved oxygen was controlled at 100% during the growth phase, compared to a base experiment (no DO control). Therefore, the results revealed that retamycin production was dependent on dissolved oxygen concentration during the growth phase, even with sufficient oxygen. On the other hand, a large oxygen supply during the production phase did not contribute to an improvement in retamycin production.

This paper presents a cybernetic structured mathematical model developed for the fermentation step of the process of production of the copolymer of polyhydroxyalkanoates by the bacteria Alcaligenes eutrophus. This process is performed in two different fermentation stages. The first emphasizes the growth of the microorganism in a batch operation without substrates limitations, while in the second, the focus is on copolymer production by a fed-batch operation in the absence of the nitrogen source. This paper presents the results of the treatment of experimental data and of preliminary parameter estimation. The fitting of the proposed model to the experimental data of a standard experiment showed a good agreement.

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.

Em regime descontínuo, o crescimento celular e a formação de 2,3-butanodiol/acetoína por Klebsiella pneumoniae sofrem inibição por concentrações iniciais de sacarose (S0) acima de 60 g/L. Sob condições não inibidoras, uma velocidade máxima de consumo de sacarose de 1,5 g/L/h foi observada. Entretanto, com S0 = 204 g/L, esta velocidade decresceu para 0,15 g/L/h. A fermentação de 204 g/L de sacarose por K. pneumoniae levou à formação de 84,3 g/L de mistura 2,3-butanodiol/acetoína, com uma conversão de 0,41 g/g e uma produtividade de 1,06 g/L/h. Um maior suprimento de oxigênio aumentou a velocidade global do processo mas reduziu a conversão em produto. Em regime descontínuo alimentado, a inibição foi evitada, tendo sido atingida uma concentração final de produtos de 80,0 g/L, com uma produtividade de 2,63 g/L/h e uma conversão de 0,37 g/g.

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.

The aim of this work was to study the influence of phosphate concentrations on glucoamylase production by the fungus Aspergillus awamori. In culture media containing cassava flour, different levels of phosphates were tested and the fungal responses to increasing levels (whether or not coupled to pH adjustment throughout the run) were assessed in terms of the resulting glucoamylase production. Phosphate increments, associated with pH readjustments throughout the run, yielded around 1,200 U/L of quite stable glucoamylase activity in the broth, while under a conventional condition (low phosphate without pH readjustment), enzymatic activity was around 350 U/L, which decayed dramatically towards the end of the cultivation

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 rheometer