UN METODO DE PRODUCIR BIOPOLIMEROS.

摘要

1496346 Soil improvement with biopolymers; purifying water AMERICAN BIOCULTURE Inc 4 Dec 1974 [4 Dec 1973] 52398/74 Headings C1B and C1C [Also in Divisions C3 and C6] Biopolymers exhibiting flocculating activity useful in coagulating solids in aqueous dispersion and in improving soil quality are prepared by cultivating unicellular green and/or non-nitrogen-fixing blue-green algae in the presence of light and in a nitrogen-deficient nutrient medium supplied with a carbon source, the nitrogen deficiency in the medium being of an order sufficient to induce the formation of the desired biopolymers, e.g. giving an algal cell nitrogen content of less than 5% by weight of the dry cell. The polymers are ethanol precipitable, include polysaccharides (anthrone reaction), are not protein in nature and have a M.W. of approx. 100,000 daltons. They are primarily extra-cellular metabolites. For coagulating, from 100 to 1000 parts by weight of the polymer is employed for every million parts of dispersed solids. For improving soil quality, I part by weight of polymer is used with 1000-5000 parts by weight of soil to form water-stable aggregates. The algae may be first cultivated to a population density of 107-108 cells/ml. of culture under conditions which are not nitrogen deficient and thereafter the algal culture (or part thereof), after dilution and transference to a second culture vessel, is further cultivated under conditions of increasing nitrogen deficiency starting from a nitrogen content of not more than 5% by weight of the dry cell. Preferred algal species are Chlorella pyrenoidosa and Chlamydomonas mexicana. In Example 5 the flocculating activity of the algal biopolymers is compared with that of polystyrene sulphonate, using aqueous dispersions of kaolin. Example 6 relates to the flocculation of screened effluent of sewage using the algal biopolymers and lime (pH 10-11). Examples 7 and 8 are directed to the production of water-stable aggregates of a dry calcareous soil (20% clay, 53% silt and 27% sand) with the aid of the biopolymers and of the improved quality of soil plots subsequent to their treatment with the biopolymers, respectively.