## 4 Discussion
Because of that, it was suggested that the increase in clinical effectiveness of IBD therapy may be achieved by processing the faecal microbiota transplants by anaerobic technique introduced by [PERSON] et al. [53]. However, controlled research evaluating the anaerobic versus the conventional processing of FMT is needed in order to decide whether the use of such a technique can bring improved results. In the study conducted by [PERSON] et al. [50], the authors compared anaerobic processing with processing carried out in the presence of oxygen. The viability of bacteria was affected the most by homogenisation of the transplant in mixers. High-speed mixing in comparison with manual homogenisation results in increased exposure to oxygen and higher damage to species susceptible to oxygen. On average, only about half of the bacteria present in faecal transplants retained their viability even after their immediate processing under strictly anaerobic conditions [50]. This correlates with the results obtained in our study that revealed 44% viability of microorganisms in FMT after its processing under aerobic conditions. With increasing time of storage, the number of viable bacteria showed a uniform decrease, and in the frozen form the number declined to 30% after 9 months of storage. Discussions involved the following question: which form of processed FMT provides better results with respect to IBD therapy, fresh or frozen? Several studies compared the rates of clinical remission after applying FMT when using fresh or frozen form of faecal microbiota for CDI treatment. Results unambiguously showed that neither anaerobic or aerobic processing nor fresh or frozen stool significantly affected the effectiveness of FMT for rCDI treatment [54]. Several other randomised studies and meta-analyses showed that both the frozen form of FMT as well as fresh FMT showed the same effectiveness with respect to clinical improvement in recurrent and refractory CDI [55; 56; 57]. These results raised the following question: to what degree are the anaerobic species, and their metabolites in particular, and also the additional important soluble and insoluble bioactive components occurring in FMT, preserved during aerobic processing? One of the factors that may play an important role in equal successfulness regarding the clinical remission rates at CDI treatment when using both ways of FMT processing (anaerobic, aerobic) may presumably involve, besides successful colonisation and the effect of faecal microbiota of the donor, also the participation of metabolites of important taxonomic bacterial representatives the \"healthy bowel markers\" in the final product. Some researchers implied that viable bacteria are needed for recolonisation of the intestine, but other studies suggested that no anaerobic bacteria are necessary for effectiveness of rCDI treatment [50; 58; 59]. However, it was discovered that an adequate proportion of their metabolites is important [60; 61; 62]. It is surprising that in the study by [PERSON] et al. [63], the authors observed equivalent or higher concentrations of all measured SCFAs in the stored lyophilised forms of stool kept at 4 \({}^{\circ}\)C for 12, 33, 60, and 130 days in comparison with the fresh stool. Samples of stool were processed and conserved using a procedure similar to the standard methodical procedure of FMT processing. Although [PERSON] et al. [48] and [PERSON] et al. [64] arrived at the same conclusion, [PERSON] et al. [65] contririwise observed lower concentrations of SCFAs in the lyophilised forms of stool. SCFAs are the main metabolite produced by intestinal microbiota during fermentation of fibres and their proportion in the digestive tract reflects the level of intestinal fermentation. However, the respective molecular ratio of SCFAs, 60:20:20 (acetate/propionate/butyrate), is constant in relatively healthy intestine, as in the large intestine section as in human stool [66].