The inulin hydrolysis by recombinant exo-inulinases: determination the optimum temperatures and activation energies

The advantages of recombinant enzymes over native include the control in a production environment, product purity and also high yield. The paper presents the determination the optimum temperatures and the activation energies for various origin recombinant exo-inulinases, among others from Aspergillus niger, A. awamori, Kluyveromyces marxianus and K. cicerisporus. The parameters were estimated based on the literature of the activity curves versus temperature for hydrolysis of inulin. It was assumed that both the hydrolysis reaction process and the deactivation process of recombinant exo-inulinase were first-order reactions by the enzyme concentration. A mathematical model describing the effect of temperature on recombinant exo-inulinase activity was used. Based on the comparison analysis, values of the activation energies $${E_{\rm a }}$$ E a were in the range from $${32.01 \pm 7.80}$$ 32.01 ± 7.80 to $${43.83 \pm 4.87}$$ 43.83 ± 4.87 kJ mol$$^{-1}$$ - 1 , the deactivation energies $${E_{\rm d }}$$ E d were in the range from $${83.93 \pm 4.82}$$ 83.93 ± 4.82 to $${352.44 \pm 14.26}$$ 352.44 ± 14.26 kJ mol$$^{-1}$$ - 1 and the optimum temperature $${T_{\rm opt }}$$ T opt were obtained in the range from $${318.91 \pm }$$ 318.91 ± 1.19 to $${328.76 \pm 0.25}$$ 328.76 ± 0.25 K.

Phosphate Enrichment of Niobium-Based Catalytic Surfaces in Relation to Reactions of Carbohydrate Biomass Conversion: The Case Studies of Inulin Hydrolysis and Fructose Dehydration

In this work, some physical mixtures of Nb2O5·nH2O and NbOPO4 were prepared to study the role of phosphate groups in the total acidity of samples and in two reactions involving carbohydrate biomass: hydrolysis of polyfructane and dehydration of fructose/glucose to 5-hydroxymethylfurfural (HMF). The acid and catalytic properties of the mixtures were dominated by the phosphate group enrichment. Lewis and Brønsted acid sites were detected by FT-IR experiments with pyridine adsorption/desorption under dry and wet conditions. Lewis acidity decreased with NbP in the composition, while total acidity of the samples, measured by titrations with phenylethylamine in cyclohexane (~3.5 μeq m−2) and water (~2.7 μeq m−2), maintained almost the same values. Inulin conversion took advantage of the presence of surfaces rich in Brønsted sites, and NbOPO4 showed the best hydrolysis activity with glucose/fructose formation. The catalyst with a more phosphated surface showed less deactivation during the dehydration of fructose/glucose into HMF.

Optimization of Inulin Hydrolysis by Penicillium lanosocoeruleum Inulinases and Efficient Conversion Into Polyhydroxyalkanoates

Graphical AbstractScheme of the developed bioprocesses.

Acid-assisted extraction and hydrolysis of inulin from chicory roots to obtain fructose-enriched extracts

Chicory (Cichorium intybus var. foliosum) roots are an agricultural residue and a low cost feedstock for the production of the platform chemical 5-Hxdroxymethylfurfural (HMF). In a first step, inulin and fructose have to be extracted from the roots. The resulting aqueous extract represents the starting material for the HMF production. In the reaction to HMF, inulin has to be hydrolyzed first to fructose. For this reason, two methods to increase the fructose content in these extracts before the reaction were investigated. This was conducted within the framework of integrating acid hydrolysis into a biorefinery process for HMF production. The first method (one-step process) was acid-assisted extraction to directly hydrolyze inulin in the course of the extraction process. Chicory roots were extracted at 60 and 80 °C at pH 2 and 4 using buffer solutions. The second approach (two-step process) was aqueous extraction at neutral pH followed by nitric acid hydrolysis of the extract at 60 and 80 °C under reduced pH. It was found that in the first approach, the pH of 2 led to a fivefold increase in the fructose content of the extract, resulting from inulin hydrolysis and corresponding to 56% of theoretical fructose yield. For the second approach, it was possible to achieve complete hydrolysis at pH below 2.5 and at 80 °C. Separating extraction and hydrolysis was found to be more suitable in terms of including this process step into a biorefinery concept for HMF production. It was possible to reduce the initial inulin content by 95%.

PRODUCTION OF OLIGOFRUCTOSE SYRUP BY ENZYMATIC HYDROLYSIS FROM INULIN-CONTAINING CHICORY SYRUP

The purpose of the work is to study the enzymatic hydrolysis of inulin-containing syrups of various purification degrees from chicory chips in the production of oligofructose to be used in dietary, diabetic and health-preventive nutrition products. It has been determined that ion exchange purification of the syrup is necessary for hydrolysis. Individual stages of ion-exchange purification are specified using a two-stage scheme: К1-А1-К2-А2 and an additional stage on the “Macronet” sorbent MN200 to stabilize pH and remove bitterness taste. Requirements for the quality of syrup for hydrolysis have been developed: pH value — 4.5–5.0; chromaticity — not more than 0.5 units opt. den.; ash — not more than 0.2%; protein — 0.5%; no bitterness taste. Optimal conditions for hydrolysis of inulin-containing syrup have been established using Novozim 960 endoinulinase (Denmark): temperature — 55–58 °C; pH — 4.7–5.2; DS (dry substance) — 19%; preparation dosage — 0.4 units. INU/g of syrup DS; time 20–24 h. A sample of oligofructose syrup was obtained using the preparation “Novozim 960.” The carbohydrate composition of oligofructose after the inulin hydrolysis was determined: fructooligosaccharides (FOS) — 70.12%; oligofructosides — 24.79%; disaccharides — 2.11%; fructose — 2.98%. Requirements for carbohydrate composition of oligofructose obtained by enzymatic hydrolysis of inulin-containing syrup have been developed: sum total of FOS and oligosaccharides — not less than 93%, sum total of di- and monosaccharides — not more than 7%.

Exo-Inulinase Production by a Catabolite Repression-Resistant Mutant Thermophilic Aspergillus tamarii-U4 in Solid State Fermentation

In this study, spores of inulinase-producing thermophilic Aspergillus tamarii were subjected to UV mutagenesis, and colonies obtained were screened for inulinase production on inulin-glucose agar. The thermal stability of the inulinase was also investigated. A mutant strain U4 was found to produce 2.8 times inulinase titre (62.1U/mL) as against the wild strain (22.2U/mL). Inulinase production by this U4 strain was also found not to be significantly (P≤0.05) affected by the presence of glucose. The inulinase produced retained 64% of its activity after incubation at 65ºC for three hours. Solid-state fermentation for inulinase production by the strain U4 showed that wheat bran supported the highest inulinase titre 218.3U/gds while banana peels supported the lowest inulinase production titre of 80.5U/gds. Further optimization of cultural parameters revealed that incubation time of 5 days, 60% initial moisture content of the substrate, 2% inoculum density 2%, temperature 55ºC and pH 4.5 were optimal for inulinase production. Under optimized conditions, inulinase titre of 426.6 U/gds was observed. The pattern of inulin hydrolysis by the inulinase revealed the presence of monosaccharide as the main product of hydrolysis. Inulinase production at elevated temperatures by the mutant Aspergillus tamarii-U4 and its catabolite resistant properties showed that the organism is a potential industrial candidate for the production of exo-acting inulinases.