Use of thixotropic biopolymers as an alternative to agar for the cultivation of microorganisms on solid media

摘要: Abstract In the petroleum and allied industries, there has been an increasing demand for reliable viable counts on fuel samples, a membrane filtration procedure, IP385/95, emulsification procedure AFNOR MO7070/92, have standardised. The former is unsuitable site use, although latter can be coupled to Dip-slide test, it inherits limitations of this procedure. methodology described was direct response need sensitive, quantitative on-site microbiological test fuel, but technology applied any aqueous non-aqueous sample. A nutritive solution, which may, if required, selective, gelled with thixotropic and/or pseudo-plastic agents instead agar. sample dispersed in gel by shaking, allowed re-set as flat horizontal layer. During incubation, colonies develop comparable colony formation ‘shake’ plates. preferred configuration fuel-testing, ca. 16 ml dispensed into screw-capped rectangular glass containers 65 capacity. sensitive redox indicator gives early indication growth. accuracy similar shake plate. Very large numbers microbes produce coloured formazan within few hours—a real time test. composition formulated so that samples emulsify completely disperse. formulation used diesel aviation kerosene; results are methods IP385/95 M07070/92. Preliminary tests water, milk, emulsions, etc. suggest will wide applications laboratory particularly on-site.