Separation of organic dust from microorganism suspensions by partitioning in aqueous polymer two-phase systems

Conidia of Penicillium brevi-compactum and Aspergillus fumigatus, sporangiospores of Rhizopus rhizopodiformis, spores of Streptomyces griseus, and bacterial cells of Bacillus subtilis were partitioned in two-phase systems consisting of dextran, polyethylene glycol, substituted positively charged sulfonylpolyethylene glycol, and water. At a pH of 2.8 in the system, the microorganisms showed 60 to 90% affinity for the upper, polyethylene glycol-rich phase, except for cells of B. subtilis, which were entirely located in the lower, dextran-rich phase. This partition behavior was used to separate microorganisms in aqueous suspensions of peat, wood fuel chip, and straw samples from organic dust impurities prior to total count by acridine orange staining and epifluorescence microscopy. Only one extraction of the interphase and lower phase was needed to separate approximately 98% of the conidia of Penicillium chrysogenum from a suspension containing peat dust.