An account is given of the development of the utilization of microalgae for food and feed with special emphasis on the advantages of algal technologies for tropical and subtropical countries. The present status of microalgae mass production is characterized with respect to technology, product properties, yields, nutrition, toxicology and economics. As a multipurpose operation, the treatment of liquid wastes with algae-bacteria systems is the most promising microalgal technology. It yields proteinaceous microbial biomass as a comparatively inexpensive byproduct of the operation of high-rate algal ponds, either at the simplified rural level or at the technically more elaborate industrial level. The aspect of hard-currency saving by employing algae-bacteria systems in sewage treatment for animal feed production is stressed.
The influence of two phytogenic surfactants on the elimination of polycyclic aromatic hydrocarbons (PAH) was studied in shaken-batch cultures of three soil bacteria under axenic conditions. At sufficiently high concentrations, quillaya saponin and soybean lecithin solubilized phenanthrene or fluoranthene efficiently. However, complete solubilization of the PAH by lecithin only doubled the maximal rate of elimination of the two PAH compounds by Pseudomonas 0259, strain MKm (Rhizomonas ?) and Mycobacterium EMI 2. By contrast, quillaya saponin did not improve PAH bioavailability, and in strain MKm it caused significant growth lags above 2.5 g/l. Simultaneously with the elimination of the PAH the bacteria utilized the surfactants as substrates for growth. Intermediate formation of PAH metabolites was noted. The results suggest that some phytogenic surfactants might improve PAH bioavailability in rhizospheres.
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