The biodegradation of tallow by Trichoderma harzianum rifai RP1
Fleming, John Patrick (2002) The biodegradation of tallow by Trichoderma harzianum rifai RP1. PhD thesis, Dublin City University.
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Wastewater, activated sludge and tallow were used as sources o f organisms in enrichment cultures to screen for species capable of degrading the hard fat, tallow. A total of 58 strains were isolated, o f which seven non-filamentous and two filamentous organisms removed greater than 20% of 20g/l tallow from batch cultures.
Optimum fat removal of 83% by the strain F2, identified as the fungus Trichoderma harzianum Rifai RP1, was observed in cultures buffered to pH 6, incubated at 25°C, shaking at 130rpm using lg/1 tallow as the sole carbon source with no added surfactant, using an inoculum of one 5-day old 8mm mycelial agar plug.
Growth followed Monod kinetics, with a ks of 0.758g/1 and pmax of 1.438 day’1. Glyceride hydrolysis was efficient, but free fatty acids, mainly palmitic, stearic and oleic acids, accumulated in the culture supernatant. Accumulation of intracellular lipid was observed, increasing during incubation to account for 35% - 55% o f biomass. Intracellular lipid was predominantly composed of triglycerides and free fatty acids. No fatty acid preference was evident in this accumulation.
In cultures with a mixture o f palmitic, stearic and oleic acids as sole carbon source, up to 97% removal was observed with 0.12g/l of the fatty acid mixture. Oleic acid was assimilated by RP1 more readily than the two saturated fatty acids. Accumulated intracellular lipid accounted for varying proportions o f biomass, from 9% to 47%. Free fatty acids were the dominant lipid class intracellularly, with lower concentrations o f triglycerides. Stearic acid accumulated in the intracellular lipid to a greater extent than palmitic or oleic acids.
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