In MSM (Figure 3), with SMX as sole C- and N-source, the removal rate of SMX was even lower. Biodegradation rates of 1.0 mg L-1 d-1 were found for Brevundimonas sp. SMXB12 while Pseudomonas sp. SMX321 showed 1.7 mg L-1 d-1. All other species showed removal rates of 1.25 mg L-1 d-1. These experiments with SMX as sole C/N-source proved that it could serve as nutrient source but with up to 2.5-fold reduced biodegradation rates. Biodegradation pattern in MSM was similar to that in MSM-CN with a lag phase of two days for the four selleck chemical isolates SMX321, 345, 348 and B12 (Figure 3A) and no lag phase for the isolates SMX 330,
331, 332, 344, and B24 starting to utilize SMX already after two days (Figure 3B). In general it was found that the five Pseudomonas spp. and the two Microbacterium spp. did not show the same biodegradation behavior. At least one selleck member of each group always showed
a lag phase while the other immediately started SMX biodegradation. As UV-AM revealed sufficient to monitor SMX biodegradation (Table 1) LC-UV measurements were only performed at the start of the experiment, day 4 and at day 10 as control measurement (Figures 3B, 4C, D). LC-UV showed that in R2A-UV all cultures removed 10 mg L-1 SMX in 4 days (Figure 2B) while in MSM-CN only Pseudomonas sp. SMX321 removed all SMX within 4 days (Figure 3C). The remaining 8 cultures still showed residual SMX concentrations from 0.4 to 7.3 mg L-1 and complete SMX elimination was achieved only at day 10 (Figure 3C, D). In MSM after 4 days SMX before was still present
in all nine cultures in concentrations above 3.6 mg L-1 and only after 10 days SMX was below the limit of detection (Figure 4C, D). LC-UV values could be compared to UV-AM values and proved this AG-881 molecular weight simple approach to be applicable for screening SMX biodegradation. Discussion and conclusions This study focused on the cultivation of pure culture SMX biodegrading organisms to perform specific biodegradation experiments. It is known that cultivation, especially on solid media, is affected with the problem described as “viable but non cultivable” (VBNC) [30, 31]. Solid media being implicitly required for the isolation of pure cultures is for sure limited in its cultivation efficiency mainly due to reduced water content and different or inappropriate nutrient conditions. Thus only a low percentage of around 1% of the active organisms in environmental samples  and around 15% from activated sludge can be cultivated [33, 34]. In this study 9 different isolates out of 110 pure cultures were obtained that showed SMX biodegradation. This quite high percentage of almost 10% was only possible with a two-step SMX-acclimation experiment that was conducted to increase the chance to cultivate SMX biodegrading organisms by applying a strong selective pressure using 10 mg L-1 SMX in the media.