Sucrose Biotransformation to Fructooligosaccharides by Aspergillus sp. N74 Free Cells

Abstract

Fructooligosaccharide production with the fructosyltransferase from free cells of the native strain Aspergillus sp. N74 at laboratory level was evaluated. The biomass of the native strain Aspergillus sp. N74 was produced in a sucrose fermentation medium and was employed in the enzymatic reaction in solutions of sucrose and phosphate buffer, where pH, temperature, and initial sucrose concentration effect were evaluated. Fructooligosaccharides and reaction subproducts were identified and quantified by high-performance liquid chromatography. The enzyme produced by the strain Aspergillus sp. N74 possessed hydrolytic and transfructosylating activities that changed with process conditions. The best transfructosylating condition was obtained at 80 min reaction time at pH 5.5, 60°C, and initial sucrose concentrations higher than 550 g L −1 , with fructooligosaccharide production of about 50% w/w (based on initial sucrose concentration) and conversion selectivity higher than 90%. In addition, the transfructosylating and hydrolytic activities ratio was of 20. The high transfructosylating activity showed by the fructosyltransferase produced from the native strain Aspergillus sp. N74 suggest considering it as an alternative for the scale-up production of fructooligosaccharides by means of the whole microorganism at bench and pilot plant levels.

Computational analysis of the fructosyltransferase enzymes in plants, fungi and bacteria

“…Ritsema et al (2006) proposed that this motif could influence the entry of the acceptor sucrose when fructose is retained in the enzyme. In that sense, fungal FTases have a "chimeric" domain that supports the findings of invertase activity in fungal FTases under certain conditions (Yun, 1996;Sangeetha et al, 2005;Sanchez et al, 2008aSanchez et al, , 2008bCaicedo et al, 2009). The analysis of this motif in fungi FTases supports our hypothesis that they were generated from an ancestral dicot invertase since they have the "chimeric" (F-and S-type) domain.…”

“…Chuankhayan et al (2010) proposed that this Leu provides important hydrophobic interactions favoring the substrate binding, while in A. oryzae N74 FTase the hydrogen bond with the Ser could be important for catalytic residue orientation (Rodriguez et al, 2010). This could in part explain the difference in yield of FOS production observed between A. oryzae and A. japanicus strains (Chien et al, 2001;Sanchez et al, 2008b;Mussatto et al, 2009). Another important change was observed with Asn and Gly residues located at the position 7 in clade VIa and VIb members, respectively.…”

“…Another significant contribution encountered is their role in drought tolerance and freezing stress (Vijn and Smeekens, 1999). FOS might also be produced by yeast and fungi like Neurospora crassa, Candida utilis, Fusarium oxysporum, Aspergillus niger, Aspergillus oryzae, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Schwanniomyces occidentallis (Sangeetha et al, 2005;Maiorano et al, 2008;Sanchez et al, 2008b).…”

“…During the last years, we have worked in the production of FOS by using an A. oryzae strain (Sanchez et al, 2008a(Sanchez et al, , 2008bCaicedo et al, 2009), and recently the ftase gene from that strain was cloned and the tertiary structure of the enzyme was modeled (Rodriguez et al, 2010). To continue the understanding and optimization of FOS production, in this study we conducted a computational analysis of reported sequences for FTases from a diverse source of organisms, such as plants, fungi and bacteria.…”

Screening of microbial isolates for extracellular fructosyltransferase production

“…The sucrose is biologically transformed into FOS either by using microorganism itself (Chien et al, 2001;Sanchez et al, 2010) or by enzymes derived from them (Fawkia et al, 2009).…”