FRUCTOOLIGOSACCHARIDES PRODUCTION FROM SUCROSE BY Aspergillus sp. N74 IN A HYBRID BIOREACTOR
Integration of life sciences & engineering
Integration of Life Sciences & Engineering - Poster (T5-P)
Keywords: Fructosyltransferase, Fructooligosaccharides, Aspergillus sp., Hybrid reactor
The batch fructooligosaccharides (FOS) production by fructosyltransferase from Aspergillus sp N74 using whole cells was studied. The biomass production and enzymatic reaction were carried out in a hybrid reactor (airlift mechanically agitated) with an operation volume was 4.5L, the airlift draft tube was conform by a stainless steel filtration module with a pore diameter of 20 m and its geometry was no-conventional, by means of this filtration module the culture medium was removed. For the enzymatic reaction, the sucrose solution was added to the reactor through a peristaltic pump, without the held biomass exposure to the environment. Two biomass concentrations 6 and 9.5 g L-1 of Aspergillus sp N74 mycelia were employed to evaluate the fructosyltransferase activity. The enzymatic reaction conditions were pH 5.5, temperature 60oC and the initial sucrose concentration was 70% (w/v); in the reactor, the superficial air velocity and agitation rate were 0.012 m s-1 and 450 r.p.m respectively. For each biomass concentration the allowed reaction time for the batch operation was 26h.
The carbohydrates were analysed by HPLC, each sample was characterized in two different columns; first by a Sugar-Pak® column for the sucrose, fructose and glucose analysis and then by a ShodexTM column for the fructooligosaccharides analysis. The composition of the produced fructooligosaccharides showed a dependence upon the reaction time and biomass concentration. In fact, 1-kestose and nystose were the FOS produced for the 6 g L-1 biomass concentration while for the 9.5 g L-1 biomass concentration was synthesized besides 1--fructofuranosyl nystose during the reaction time.
The FOS yield in batch operation for the 6 g L-1 biomass concentration was 69% (43% 1-kestose and 26% nystose) while for the 9.5 g L-1 biomass concentration the highest FOS yield was 76% (43% 1-kestose, 29% nystose and 4% 1-B-fructofuranosyl nystose) gotten in the first 4h of reaction but at the end of the reaction time (~26h) the FOS yield decrease to a 57% (18% 1-kestose, 33% nystose and 6% 1-B-fructofuranosyl nystose), this phenomena could be caused by the enzyme hydrolytic activity over the FOS and its ability to form sucrose from free glucose and fructose.
It is noticed that at 9.5 g L-1 biomass concentration the control of the reaction time is very important to get an important sucrose bioconversion to FOS and control of their composition. The designed reactor allowed to get a high cell density culture of the fungus and also to make a separation process with out the exposure to contamination of the held biomass. The results gotten with the design reactor and the fructosyltransferase enzyme activity from the native strain Aspergillus sp N74 suggest that this process can be considered as an industrial alternative for the fructooligosaccharides production.
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Presented Wednesday 19, 13:30 to 15:00, in session Integration of Life Sciences & Engineering - Poster (T5-P).
