In this study, the glycerol solutions were fermented using Lactobacillus casei bacteria. The broths were pre-treated by microfiltration, followed by a further separation with nanofiltration. The latter process was carried out in two stages, using the NF270 and NF90 membranes, respectively. The concentrates thus obtained were enriched with citric acid (first stage) and then with lactic acid and glycerol (second stage). By means of SEM and AFM microscopy, as well as ATR-FTIR analysis, the intensity of membrane-fouling was studied. The colloidal fouling and bio-fouling caused a more than two-fold decrease in the permeate flux during microfiltration of the broth. This pre-treatment stage was effective, and a permeate turbidity of less than 0.2 NTU was obtained. However, the nanofiltration membranes exhibited a 30 % flux decline over the course of the process, mainly due to the organic fouling.

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In this work, the glycerol fermentation was carried out using Citrobacter freundii bacteria. The infl uence of glycerol and metabolites concentrations, and the pH changes on the effi ciency of 1,3-propanediol production, during batch and fed-batch processes, was presented. The nanofi ltration was used for the separation of obtained post-fermentation solutions. The resulted 1,3-PD solutions were signifi cantly desalted, which may facilitate further downstream processes during 1,3-PD production.

In this work the studies were performed on the intensity of fouling of the membrane NF90 and NF270 depending on the value of dynamic contact angle, previously determined for these membrane. The NF membranes were used for the separation of broth obtained during the fermentation of glycerol by Lactobacillus casei bacteria. The measurements of dynamic contact angle were carried out using the Wilhelmy plate method. Taped membranes samples (support layer to support layer), wetted for 2 days in deionized water prior to testing, were used to study the contact angle of top layer and its organic fouling. Using deionized water; the contact angle values equal to [27][28][29][30] o and 53-57 o for NF270 and NF90, respectively, were obtained. As a consequence of adsorption of organic compound on the membrane surfaces, the contact angle obtained for both fouled membranes was about 55-56 o , and this value was closer to the contact angle of non-fouled NF90 membrane. Therefore, the NF90 membrane was more resistant to organic fouling during the separation of broth.

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