The production of potentially prebiotic oligosaccharides by Leucosporidium scottii Y - 1450

[摘要] English: Prebiotic oligosaccharides are gaining interest in the food, poultry and pharmaceutical industries due to their health benefits. These include prevention of specific allergies, improved calcium absorption, reduction in the duration, incidence, and symptoms of traveller's diarrhoea, alleviation of irritable bowel syndrome (IBS) symptoms, increased satiety and reduced appetite. In the food industry they are responsible for modifying food flavour, they are considered as low energy ingredients alleviating obesity and have a high water-holding capacity, low sweetness and an anti-staling effect. The main objectives of this study were to produce, purify and identify oligosaccharides from Leucosporidium scottii Y-1450.Leucosporidium scottii Y-1450 produced neofructooligosaccharides during growth on sucrose. Two trisaccharides and a tetrasaccharide were produced. The highest oligosaccharide concentration obtained was 33.7 g l-¹ after 22 h of cultivation. A maximum specific growth rate, maximum volumetric rate of oligosaccharide production, and maximum yield coefficient for the production of oligosaccharides (oligosaccharides produced/sucrose assimilated) of 0.28 h-¹, 1.53 g (l h)-¹ and 0.58 were obtained respectively. In addition to the products of interest, glucose, fructose and sucrose were also present in the supernatant.Purification of the supernatant containing mono-, di and oligosaccharides was done by preparative HPLC. A total oligosaccharide concentration of 2.9 g l-¹ was obtained after purification from 7.8 ml of supernatant. The first unknown trisaccharide was not successfully purified as it overlapped with the second trisaccharide. The second trisaccharide and the tetrasaccharide were successfully purified with percentage recoveries of 0.12 % and 15.3 % respectively.LCMS identification using Electrospray Mass Spectrometry (ESMS) of the supernatant showed the presence of three oligosaccharides with m/z of 503.4, 539.3 and 665.5 Da, respectively. This was later followed by structural identification of the tetrasaccharide by NMR.Results from MALDI-TOF and NMR analysis confirmed the presence of two oligosaccharides present in the tetrasaccharide fraction, a trisaccharide (from the breakdown of the tetrasaccharide) identified as 1-kestose (α-Glcp-1-2-β-Fruf-1-2-β-Fruf) and a tetrasaccharide identified as neonystose (β-Fruf-2-6-α-Glcp-1-2-β-Fruf-1-2-β-Fruf).A two level fractional factorial screening design was used to investigate oligosaccharide production, with sucrose concentration, cell concentration, pH and temperature as the factors and maximum oligosaccharide concentration, yield coefficient and productivity as the responses. The highest concentration, yield coefficient and productivity of oligosaccharides were obtained at 200 g l-¹ sucrose, 8 g l-¹ cell concentration, pH 7 and 20 °C. ANOVA analysis indicated sucrose concentration as a highly significant main effect for all three responses while the interaction sucrose concentration*cell concentration was identified as a significant interaction for the responses. Temperature was an insignificant factor for all three responses.This study highlighted the feasibility of the production of neoFOS with possible prebiotic potential from sucrose by Leucosporidium scottii.

[发布机构] University of the Free State