One-Step Bioprocess of Inulin to Product Inulo-Oligosaccharides Using Bacillus subtilis Secreting an Extracellular Endo-Inulinase

Efficient production of inulo-oligosaccharides from inulin by exo- and endo-inulinase co-immobilized onto a self-assembling protein scaffold

Inulin can be hydrolyzed by inulinases to yield inulo-oligosaccharides (IOSs), which have great application potential in the food and nutraceutical industries. However, conventional enzymatic production of IOSs is limited by long hydrolysis times and poor thermo-stability of inulinases. Here, the self-assembling protein scaffold EutM was engineered to co-immobilize exo-inulinase (EXINU) and endo-inulinase (ENINU) for synergistic hydrolysis of inulin to produce IOSs with 3 to 5 monosaccharide units (DP3-5 IOSs). The immobilization of EXINU/ENINU onto the EutM scaffold resulted in an increase of catalytic efficiency, a 65% increase of the V_max of ENINU, as well as an increase of thermo-stability, with 4.26-fold higher residual activity of EXINU after 22 h-incubation at 50 °C. After optimization, two efficient production protocols were obtained, in which the yield and productivity of DP3-5 IOSs reached 80.38% and 70.86 g·(L·h)^-1, respectively, which were at a high level in similar studies. Overall, this study provides an attractive self-assembling protein platform for the co-immobilization of inulinases, as well as optimized bioprocesses with great promise for the industrial production of DP3-5 IOSs.

Understanding the interactive influence of hydrolytic conditions on biocatalytic production of fructooligosaccharides from inulin

Statistical optimization of hydrolytic conditions for the production of fructooligosaccharides (FOSs) from pure inulin using Aspergillus tritici endoinulinase was carried out in a batch system. FOSs yield 99.19% was obtained under the optimized hydrolytic conditions i.e. inulin concentration (7.3%), enzyme load (65 IU), hydrolysis time (13 h) and agitation (100 rpm). The closeness of value of co-efficient of determination (R²) to 1, good agreement between model's predicted and experimental values, low percentage error (<5%), high adequate precision (>4%) and F value (11,634.32), and low Lack of fit (0.60) of the designed model authenticates its fitness. High substrate concentration, low enzyme load and short hydrolysis span justifies efficiency of developed process for the preparation of FOSs from inulin using fungal endoinulinase. TLC chromatographic and densitometry studies confirmed the synthesis of short-chain length FOSs. FOSs preparation contained 33.85% GF2 (ketose), 24.50% GF3 (nystose), 7.26% GF4 (fructofuranosylnystose) and 33.58% FOSs of DP5-9.

Investigating the effect of different inulin-rich substrate preparations from Jerusalem artichoke (Helianthus tuberosus L.) tubers on efficient inulooligosaccharides production

Commercial production of inulooligosaccharides (IOS) relies largely on chicory roots. However, Jerusalem artichoke (JA) tubers provide a suitable alternative due to their high inulin content and low cultivation requirements. In this study, three inulin-rich substrate preparations from JA were investigated to maximize IOS production, namely powder from dried JA tuber slices (Substrate 1), solid residues after extracting protein from the JA powder (Substrate 2) and an inulin-rich fraction extracted from protein extraction residues (Substrate 3). The preferred temperature, pH and inulin substrate concentration were determined after which enzyme dosage and extraction time were optimized to maximize IOS extraction from the three substrates, using pure chicory inulin as benchmark. Under the optimal conditions, Substrate 3 resulted in the highest IOS yield of 82.3% (w/w_inulin). However, IOS production from the Substrate 1 proved more efficient since it renders the highest overall IOS yield (mass of IOS per mass of the starting biomass). In the case of co-production of protein and IOS from the JA tuber in a biorefinery concept, IOS production from the Substrate 2 is preferred since it reduces the inulin losses incurred during substrate preparation. For all the inulin-rich substrates studied, an enzyme dosage of 14.8 U/g_inulin was found to be optimal at reaction time less than 6 h. JA tuber exhibited excellent potential for commercial production of IOS with improved yield and the possible advantage of a reduced biomass cost.

Optimization and characterization of oligosaccharides production from citrus peel waste resource using Aspergillus niger 1805

Oligosaccharides have many growth-promoting properties for crops and are effective for fighting off various diseases in agriculture. Producing oligosaccharides from waste fruit peel by using food microorganisms will be a potential approach to provide the high-value products for sustainable development of green agriculture. Aspergillus niger 1805 was isolated from citrus peel and identified by internal transcribed spacer (ITS1-ITS4) sequencing. A. niger 1805 grew well only with waste citrus peel (WCP) as the sole medium. >50% WCP was degraded into oligosaccharides by fermentation with A. niger at 37 °C, pH 5.0 and 4 mM Ca²⁺ within 72 h, and oligosaccharide yield rate of >40%. Most oligosaccharides were in the form of Nano-size particles [10-500 nm]. Kolmogorov-Smirnov Goodness of Fit Test (KS test) showed that the distribution of the oligosaccharide micro-particles fitted a lognormal model (p > .05). Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analysis showed that the oligosaccharides were mainly comprised of glucose polymer with degrees of polymerization (DP) of 4-17. A. niger 1805 is a potential tool to produce oligosaccharides from WCP.

Preparation of Cross-Linked Enzyme Aggregates (CLEAs) of an Inulosucrase Mutant for the Enzymatic Synthesis of Inulin-Type Fructooligosaccharides

Fructooligosaccharides are well-known carbohydrate molecules that exhibit good probiotic activity and are widely used as sweeteners. Inulin-type fructooligosaccharides (IFOs) can be synthesized from sucrose using inulosucrase. In this study, cross-linked enzyme aggregates (CLEAs) of Lactobacillus reuteri 121 inulosucrase (R483A-LrInu) were prepared and used as a biocatalyst for IFOs production. Under optimum conditions, R483A-LrInu CLEAs retained 42% of original inulosucrase activity. Biochemical characterization demonstrated that the optimum pH of inulosucrase changed from 5 to 4 after immobilization, while the optimum temperature was unchanged. Furthermore, the pH stability and thermostability of the R483A-LrInu CLEAs was significantly improved. IFOs product characterization indicated that the product specificity of the enzyme was impacted by CLEA generation, producing a narrower range of IFOs than the soluble enzyme. In addition, the R483A-LrInu CLEAs showed operational stability in the batch synthesis of IFOs.

Technological Aspects of the Production of Fructo and Galacto-Oligosaccharides. Enzymatic Synthesis and Hydrolysis

Fructo- and galacto-oligosaccharides (FOS and GOS) are non-digestible oligosaccharides with prebiotic properties that can be incorporated into a wide number of products. This review details the general outlines for the production of FOS and GOS, both by enzymatic synthesis using disaccharides or other substrates, and by hydrolysis of polysaccharides. Special emphasis is laid on technological aspects, raw materials, properties, and applications.