Technological mapping and trends in photobioreactors for the production of microalgae.

Photobioreactors (PBRs) are equipment of central importance for the massive cultivation of microalgae, providing controlled conditions for high cell productivity. There are a few popular PBR designs, with contrasting advantages and limitations, such as poor light distribution, mass transfer, or hydrodynamic behavior. Due to the environmental concerns in recent decades and the discovery of new, useful microalgal metabolites, the interest in finding alternatives to solve technological bottlenecks of PBRs has intensified. In this process, new geometries, materials, and modes of light supply were developed, generating a significant scientific and technological output, reported in papers and patents. We present a technological landscape analysis of photobioreactor design, focusing on improvements of the classical geometries and trends in industrial photobioreactors. The analysis of 412 patent documents showed a surge in innovation filing since 2005 and a reduction in the number of new documents along the last decade. The recent efforts in design improvement, the leading countries, institutes and companies that innovate, and the trends in PBR technology are presented and discussed.

Improvement of Sporobolomyces ruberrimus carotenoids production by the use of raw glycerol.

The red yeast Sporobolomyces ruberrimus H110 was able to use glycerol as a carbon source. The highest concentration (0.51gL(-1)) and productivity (0.0064gL(-1)h(-1)) of carotenoids were achieved when raw glycerol from biodiesel production, containing around 1gL(-1) of fatty acids, was used as the carbon source, which represented increases of 27% and 1.5×, respectively, in relation to pure glycerol. Mass spectrometry analysis led to the identification of four carotenoids in the fermented samples, torularhodin, torulene, ß-carotene and γ-carotene. The use of raw glycerol also enhanced the proportion of torularhodin (69% against 59% in pure glycerol). The addition of individual fatty acids (palmitic, stearic, oleic and linoleic acids) to pure glycerol resulted in increases between 15% and 25% in maximum concentration and between 1.6× and 2.0× in productivity of carotenoids. The presence of palmitic and oleic acids increased the torularhodin proportion to 66%.

Influence of airflow intensity on phytase production by solid-state fermentation.

Phytase production by Aspergillus niger F3 by solid state fermentation (SSF) on citrus peel was evaluated at pilot scale under different aeration conditions. The best airflow intensity was 1 VkgM (Lair kg medium(-1) min(-1)), which allowed to produce 65 units of phytases per gram in dry basis (65 Ug(-1) d.b.) as it removed the metabolic heat generated by the microorganism, Agitation did not improve heat removal. Airflow intensity was considered as scale-up criterion. When the airflow intensity was maintained at 1 VkgM for SSF with 2 and 20 kg of medium, the kinetics parameters for biomass and enzyme concentration at the end of fermentation differed by less than 2. The air flow intensity was required to maintain the temperature and cool the SSF and to provide oxygen for microbial growth. Air flow intensity is a key a factor that must be considered when scale-up of SSF is attempted.