Producing with carrier material, lyophilisation and determining shelf life of the mixed culture adapted for the wastewater treatment system

In this thesis, the preservation of a consortium constitued by 16 bacteria was carried out with trefoil as a carrier material and silica, skim milk and polyvinyl alcohol as preservative materials. These bacteria were selected for their high effectiveness for degrading terephthalic acid (tpa), 4-carboxybenzaldehyde (4-cba) and p-toluic acid (p-tol). The inoculum was lyophilized with an appropriate quantity of trefoil supplemented by one of the preservative compounds and stored at +4 ° C o +27 ° C for 12 months. The shelf life and biodegradation efficiency of TPA, 4-CBA and pTol were evaluated on the 1st, 3rd, 6th, 9th and 12th month of incubation. The results showed that the trefoil+skim milk mixture was the best conservative composition at +4 °C. After the biodegradation studies, the toxicity of the residual TPA, 4-CBA and pTol were performed by using Microtox Model 500 analyzer. It was found that the EC50 was below the threshold value for all of the residual hydrocarbons. The quantity of the microorganisms in the consortium were evaluated by qPCR method after 12 months of conservation. The results recorded that Comamonas testosteroni, Raoultella planticola and Pseudomonas putida were the most abundance bacteria in the mixture of trefoil+skim milk at +4 °C.