Adjustment of the Operational Parameters of an Unconventional Integrated and Illuminated Internally Photobioreactor (ILI-PBR) for the Batch Autotrophic Cultivation of the Chlorella minutissima, Using the Taguchi Method.

Microalgae crops targeting biotechnological applications are conducted in photobioreactors, which allow the adjustment and control of parameters of luminosity, agitation and mixing in the cultivation medium to promote better cell growth and accumulation of metabolites. In this sense, the present work used the Taguchi method to find the best adjustment of the operational parameters of an unconventional photobioreactor denominated internally illuminated integrated photobioreactor (ILI-PBR) with LED light aiming at elevating the biomass concentration, volumetric biomass productivity, and volumetric lipid productivity of Chlorella minutissima microalgae cultivated under autotrophic regime. The effects of the factors were evaluated: illumination (blue, white and red); photoperiod (12 h light:12 h dark, 1 h light:1 h dark, and 24 h clear:0 h dark); aeration (0, 3 vvm, 0.4 vvm, and 0.5 vvm); and recirculation flow rate of cultivation medium (5 L min-1, 6.5 L min-1, and 9 L min-1) on the variable responses: biomass concentration, biomass volumetric productivity, lipid content, and volumetric lipid productivity. The use of the Taguchi method allowed the increase of biomass concentration, volumetric biomass productivity, and volumetric lipid productivity in the biomass of Chlorella minutissimain 8.6%, 42%, and 143%, respectively, with the adjustment of the operational parameters of the photobioreactor used.

Oxygen supply in Bacillus thuringiensis fermentations: bringing new insights on their impact on sporulation and δ-endotoxin production.

The growth kinetics, sporulation, and toxicity of Bacillus thuringiensis var. israelensis were evaluated through the analysis of batch cultures with different dissolved oxygen (DO) profiles. Firstly, DO was maintained constant at 5%, 20%, or 50% throughout fermentation in order to identify the most suitable one to improve the main process parameters. Higher biomass concentration, cell productivity, and cell yield based on glucose were obtained with 50% DO. The higher aeration level also resulted in higher spore counts and markedly improved the toxic activity of the fermentation broth, which was 9-fold greater than that obtained with 5% DO (LC(50) of 39 and 329 mg/L, respectively). Subsequently, using a two-stage oxygen supply strategy, DO was kept at 50% during the vegetative and transition phases until the maximum cell concentration was achieved. Then, DO was changed to 0%, 5%, 20%, or 100% throughout sporulation and cell lysis phases. The interruption of oxygen supply strongly reduced the spore production and thoroughly repressed the toxin synthesis. On the contrary, when DO was raised to 100% of saturation, toxic activity increased approximately four times (LC(50) of 8.2 mg/L) in comparison with the mean values reached with lower DO levels, even though spore counts were lower than that from the 50% DO assay. When pure oxygen was used instead of normal air, it was possible to obtain 70% of the total biomass concentration achieved in the air assays; however, cultures did not sporulate and the toxin synthesis was consequently suppressed.

Obtençäo de 2, 3-butanodiol a partir de hidrolisado hemicelulósico de eucalipto em regime descontínuo alimentado / Obtention of 2, 3-butanediol from eucalyptus hemicellulosic hydrolysate for fedbacth process

O presente trabalho estuda o processo fermentativo de produçÝo de 2, 3-butanodiol, a partir de hidrolisado hemicelulósico de eucalipto, empregando a bactéria Klebsiella pneumoniae. Primeiramente foram comparados diversos tratamentos para a remoçÝo de inibidores do crescimento bacteriano presentes na matéria-prima, verificando-se a necessidade de se combinar a precipitaçÝo por variaçÝo do pH com a adsorçÝo por carvÝo ativo. Em seguida estudou-se as condiçSes de fermentaçÝo para a conduçÝo do processo em regime descontínuo alimentado em reator, o qual se mostrou mais eficiente que o regime descontínuo em frascos agitados. Finalmente avaliou-se a influência da concentraçÝo de substrato do meio de alimentaçÝo ('S IND. i') e da vazÝo de alimentaçÝo (phi), sobre a cinética do processo