Biotechnological potential of inulin for bioprocesses

Inulin: Properties, health benefits and food applications

Inulin is a water soluble storage polysaccharide and belongs to a group of non-digestible carbohydrates called fructans. Inulin has attained the GRAS status in USA and is extensively available in about 36,000 species of plants, amongst, chicory roots are considered as the richest source of inulin. Commonly, inulin is used as a prebiotic, fat replacer, sugar replacer, texture modifier and for the development of functional foods in order to improve health due to its beneficial role in gastric health. This review provides a deep insight about its production, physicochemical properties, role in combating various kinds of metabolic and diet related diseases and utilization as a functional ingredient in novel product development.

Efficient Conversion of Inulin to Inulooligosaccharides through Endoinulinase from Aspergillus niger

Inulooligosaccharides (IOS) represent an important class of oligosaccharides at industrial scale. An efficient conversion of inulin to IOS through endoinulinase from Aspergillus niger is presented. A 1482 bp codon optimized gene fragment encoding endoinulinase from A. niger DSM 2466 was cloned into pPIC9K vector and was transformed into Pichia pastoris KM71. Maximum activity of the recombinant endoinulinase, 858 U/mL, was obtained at 120 h of the high cell density fermentation process. The optimal conditions for inulin hydrolysis using the recombinant endoinulinase were investigated. IOS were harvested with a high concentration of 365.1 g/L and high yield up to 91.3%. IOS with different degrees of polymerization (DP, mainly DP 3-6) were distributed in the final reaction products.

Expression of exo-inulinase gene from Aspergillus niger 12 in E. coli strain Rosetta-gami B (DE3) and its characterization

Inulin is a linear carbohydrate polymer of fructose subunits (2-60) with terminal glucose units, produced as carbon storage in selected plants. It cannot directly be taken up by most microorganisms due to its large size, unless prior hydrolysis through inulinase enzymes occurs. The hydrolyzed inulin can be taken up by microbes and/or recovered and used industrially for the production of high fructose syrup, inulo-oligosaccharides, biofuel, and nutraceuticals. Cell-free enzymatic hydrolysis would be desirable for industrial applications, hence the recombinant expression, purification and characterization of an Aspergillus niger derived exo-inulinase was investigated in this study. The eukaroyototic exo-inulinase of Aspergillus niger 12 has been expressed, for the first time, in an E. coli strain [Rosetta-gami B (DE3)]. The molecular weight of recombinant exo-inulinase was estimated to be ∼81 kDa. The values of Km and Vmax of the recombinant exo-inulinase toward inulin were 5.3 ± 1.1 mM and 402.1 ± 53.1 µmol min(-1)  mg(-1) protein, respectively. Towards sucrose the corresponding values were 12.20 ± 1.6 mM and 902.8 ± 40.2 µmol min(-1)  mg(-1) protein towards sucrose. The S/I ratio was 2.24 ± 0.7, which is in the range of native inulinase. The optimum temperature and pH of the recombinant exo-inulinase towards inulin was 55°C and 5.0, while they were 50°C and 5.5 towards sucrose. The recombinant exo-inulinase activity towards inulin was enhanced by Cu(2+) and reduced by Fe(2+) , while its activity towards sucrose was enhanced by Co(2+) and reduced by Zn(2+) . © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:629-637, 2016.

Characterization of an exo-inulinase from Arthrobacter: a novel NaCl-tolerant exo-inulinase with high molecular mass

A glycoside hydrolase family 32 exo-inulinase gene was cloned from Arthrobacter sp. HJ7 isolated from saline soil located in Heijing town. The gene encodes an 892-residue polypeptide with a calculated mass of 95.1 kDa and a high total frequency of amino acid residues G, A, and V (30.0%). Escherichia coli BL21 (DE3) cells were used as hosts to express the exo-inulinase gene. The recombinant exo-inulinase (rInuAHJ7) showed an apparently maximal activity at pH 5.0-5.5 and 40-45°C. The addition of 1.0 and 10.0 mM Zn(2+) and Pb(2+) had little or no effect on the enzyme activity. rInuAHJ7 exhibited good salt tolerance, retaining more than 98% inulinase activity at a concentration of 3.0%-20.0% (w/v) NaCl. Fructose was the main product of inulin, levan, and Jerusalem artichoke tubers hydrolyzed by the enzyme. The present study is the first to report the identification and characterization of an Arthrobacter sp exo-inulinase showing a high molecular mass of 95.1 kDa and NaCl tolerance. These results suggest that the exo-inulinase might be an alternative material for potential applications in processing seafood and other foods with high saline contents, such as marine algae, pickles, and sauces.

Direct conversion of pretreated straw cellulose into citric acid by co-cultures of Yarrowia lipolytica SWJ-1b and immobilized Trichoderma reesei mycelium

The immobilized cellulase-producing mycelium of Trichoderma reesei was found to produce 2.9 U/ml of cellulase activity within 144 h while 2.1 U/ml of cellulase activity was produced within 120 h by the free mycelium of the same strain. When the immobilized mycelium of T. reesei was co-cultivated with the free cells of Yarrowia lipolytica SWJ-1b in flask, Y. lipolytica SWJ-1b could yield 10.7 g/l of citric acid and 3.9 g/l of isocitric acid from 40.0 g/l pretreated straw within 240 h. Under the similar conditions, Y. lipolytica SWJ-1b could yield 32.8 g/l of citric acid and 4.7 g/l of isocitric acid from 40.0 g/l pretreated straw supplemented with 20.0 g/l glucose within 288 h. When the co-cultures were grown in 10-l fermentor, Y. lipolytica SWJ-1b could yield 83.4 g/l of citric acid and 8.7 g/l of isocitric acid from 100.0 g/l of pretreated straw supplemented with 50.0 g/l glucose within 312 h.

Genetic Modification of the Marine-Isolated Yeast Aureobasidium melanogenum P16 for Efficient Pullulan Production from Inulin

In this study, in order to directly and efficiently convert inulin into pullulan, the INU1 gene from Kluyveromyces maximum KM was integrated into the genomic DNA and actively expressed in the high pullulan producer Aureobasidium melanogenum P16 isolated from the mangrove ecosystem. After the ability to produce pullulan from inulin by different transformants was examined, it was found that the recombinant strain EI36, one of the transformants, produced 40.92 U/ml of inulinase activity while its wild-type strain P16 only yielded 7.57 U/ml of inulinase activity. Most (99.27 %) of the inulinase produced by the recombinant strain EI36 was secreted into the culture. During the 10-l fermentation, 70.57 ± 1.3 g/l of pullulan in the fermented medium was attained from inulin (138.0 g/l) within 108 h, high inulinase activity (42.03 U/ml) was produced within 60 h, the added inulin was actively hydrolyzed by the secreted inulinase, and most of the reducing sugars were used by the recombinant strain EI36. This confirmed that the genetically engineered yeast of A. melanogenum strain P16 was suitable for direct pullulan production from inulin.

Rapid and efficient bioconversion of chicory inulin to fructose by immobilized thermostable inulinase from Aspergillus tubingensis CR16

Background

Fructose, a monosaccharide, has gained wide applications in food, pharmaceutical and medical industries because of its favourable properties and health benefits. Biocatalytic production of fructose from inulin employing inulinase is the most promising alternative for fructose production. For commercial production, use of immobilized inulinase is advantageous as it offers reutilization of enzyme and increase in stability. In order to meet the demand of concentrated fructose syrup, inulin hydrolysis at high substrate loading is essential.

Results

Inulinase was immobilized on chitosan particles and employed for fructose production by inulin hydrolysis. Fourier transform infrared spectroscopy (FTIR) analysis confirmed linkage of inulinase with chitosan particles. Immobilized biocatalyst displayed significant increase in thermostability at 60 and 65 °C. Statistical model was proposed with an objective of optimizing enzymatic inulin hydrolytic process. At high substrate loading (17.5 % inulin), using 9.9 U/g immobilized inulinase at 60 °C in 12 h, maximum sugar yield was 171.1 ± 0.3 mg/ml and productivity was 14.25 g/l/h. Immobilized enzyme was reused for ten cycles. Raw inulin from chicory and asparagus was extracted and supplied in 17.5 % for enzymatic hydrolysis as a replacement of pure inulin. More than 70 % chicory inulin and 85 % asparagus inulin were hydrolyzed under optimized parameters at 60 °C. Results of high performance liquid chromatography confirmed the release of fructose after inulin hydrolysis.

Conclusions

The present findings prove potentiality of immobilized thermostable inulinase from Aspergillus tubingensis CR16 for efficient production of fructose syrup. Successful immobilization of inulinase on chitosan increased its stability and provided the benefit of enzyme reutilization. Box-Behnken design gave a significant model for inulin hydrolysis. Extraction of raw inulin from chicory and asparagus and their enzymatic hydrolysis using immobilized inulinase suggested that it can be a remarkable cost-effective process for large-scale fructose production.

Analysis of cell growth dynamics of Pediococcus acidilactici in the presence of inulin in an optimized microenvironment

The present investigation deals with the optimization of cell growth rate of the candidate probiotic Pediococcus acidilactici in the presence of the specific prebiotic inulin. Three independent variables viz. concentration of inulin, concentration of glucose and pH have been selected for optimization study using response surface methodology. Theoretical analysis indicates that the maximum cell growth rate occurs at pH 7, 20 g/dm(3) concentration of inulin and 20 g/dm(3) concentration of glucose. Validation of these values has been done through a set of programmed experiments. Studies on cell dynamics in the presence of different concentrations of inulin have also been carried out to identify any limitation on the initial inulin concentration. Results clearly indicate that cell growth is enhanced with the increase in inulin concentration. However, there is a critical value of the prebiotic concentration (20 g/dm(3) inulin) beyond which the cell growth is inhibited. A summative type growth model has been proposed to explain the growth behaviour of P. acidilactici in the presence of the dual substrate, i.e. glucose and inulin. While growth on glucose follows Monod model, Haldane-type substrate-inhibited growth model holds good for growth on inulin. Intrinsic kinetic parameters for all the model equations have been determined experimentally.

Comparison of properties of new sources of partially purified inulin to those of commercially pure chicory inulin

Newly developed inulin powders were prepared from roots of Asparagus falcatus (AF) and Taraxacum javanicum (TJ) plants grown in Sri Lanka. Inulin content, analyzed by enzymatic spectrophotometric as well as high-performance liquid chromatographic methods, showed that AF and TJ inulin powders contain 65.5% and 45.4% (dry wt) inulin, respectively, compared with 72% dry wt in the commercially available chicory inulin. Treating the AF and TJ inulin powders using ion exchange techniques significantly (P < 0.05) reduced their contents of micro (Zn, Cu, Mn, Fe) and macro (Na, K, Ca, Mg) elements. Enzymatic hydrolysis of inulin into fructose and glucose by fructanase, and FT-IR analyses proved that the developed AF and TJ inulins have characteristic molecular composition similar to commercial inulin. TJ inulin contained significantly (P < 0.05) greater amounts of total phenolics (4.37 mg GAE/g), total flavonoids (2.79 mg QE/g), and antioxidant capacity (833.11 mM TE/g) than AF inulin, which contained 1.33 mg GAE/g of total phenolics, 0.43 mg QE/g of total flavonoids, and 406.26 mM TE/g antioxidant capacity. The current study suggests that the newly developed inulin from AF and TJ roots could be used as an alternative commercial source of inulin for the food industry.

Invertase Suc2-mediated inulin catabolism is regulated at the transcript level in Saccharomyces cerevisiae

Background

Invertase Suc2 was recently identified as a key hydrolase for inulin catabolism in Saccharomyces cerevisiae, whereas the Suc2 activity degrading inulin varies greatly in different S. cerevisiae strains. The molecular mechanism causing such variation remained obscure. The aim of this study is to investigate how Suc2 activity is regulated in S. cerevisiae.

Results

The effect of SUC2 expression level on inulin hydrolysis was investigated by introducing different SUC2 genes or their corresponding promoters in S. cerevisiae strain BY4741 that can only weakly catabolize inulin. Both inulinase and invertase activities were increased with the rising SUC2 expression level. Variation in the promoter sequence has an obvious effect on the transcript level of the SUC2 gene. It was also found that the high expression level of SUC2 was beneficial to inulin degradation and ethanol yield.

Conclusions

Suc2-mediated inulin catabolism is regulated at transcript level in S. cerevisiae. Our work should be valuable for engineering advanced yeast strains in application of inulin for ethanol production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-015-0243-3) contains supplementary material, which is available to authorized users.

Identification of a recombinant inulin fructotransferase (difructose dianhydride III forming) from Arthrobacter sp. 161MFSha2.1 with high specific activity and remarkable thermostability

Difructose dianhydride III (DFA III) is a functional carbohydrate produced from inulin by inulin fructotransferase (IFTase, EC 4.2.2.18). In this work, an IFTase gene from Arthrobacter sp. 161MFSha2.1 was cloned and expressed in Escherachia coli. The recombinant enzyme was purified by metal affinity chromatography. It showed significant inulin hydrolysis activity, and the produced main product from inulin was determined as DFA III by nuclear magnetic resonance analysis. The molecular mass of the purified protein was calculated to be 43 and 125 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, respectively, suggesting the native enzyme might be a homotrimer. The recombinant enzyme showed maximal activity as 2391 units/mg at pH 6.5 and 55 °C. It displayed the highest thermostability among previously reported IFTases (DFA III forming) and was stable up to 80 °C for 4 h of incubation. The smallest substrate was determined as nystose. The conversion ratio of inulin to DFA III reached 81% when 100 g/L inulin was catalyzed by 80 nM recombinant enzyme for 20 min at pH 6.5 and 55 °C. All of these data indicated that the IFTase (DFA III forming) from Arthrobacter sp. 161MFSha2.1 had great potential for industrial DFA III production.

The prospects of Jerusalem artichoke in functional food ingredients and bioenergy production

Jerusalem artichoke, a native plant to North America has recently been recognized as a promising biomass for bioeconomy development, with a number of advantages over conventional crops such as low input cultivation, high crop yield, wide adaptation to climatic and soil conditions and strong resistance to pests and plant diseases. A variety of bioproducts can be derived from Jerusalem artichoke, including inulin, fructose, natural fungicides, antioxidant and bioethanol. This paper provides an overview of the cultivation of Jerusalem artichoke, derivation of bioproducts and applicable production technologies, with an expectation to draw more attention on this valuable crop for its applications as biofuel, functional food and bioactive ingredient sources.

Liquid phase adsorption behavior of inulin-type fructan onto activated charcoal

This study describes liquid phase adsorption characteristics of inulin-type fructan onto activated charcoal. Batch mode experiments were conducted to study the effects of pH, contact time, temperature and initial concentration of inulin. Nearly neutral solution (pH 6-8) was favorable to the adsorption and the equilibrium was attained after 40 min with the maximum adsorption Qmax 0.182 g/g (adsorbate/adsorbent) at 298 K. The experimental data analysis indicated that the adsorption process fitted well with the pseudo-second-order kinetic model (R(2) = 1) and Langmuir isotherms model (R(2) > 0.99). Thermodynamic parameters revealed that the adsorption process was spontaneous and exothermic with a physical nature. Inulin desorption could reach 95.9% using 50% ethanol solution and activated charcoal could be reused without significant losses in adsorption capacity. These results are of practical significance for the application of activated charcoal in the production and purification of inulin-type fructan.

From fructans to difructose dianhydrides

Fructans are the polymers of fructose molecules, normally having a sucrose unit at what would otherwise be the reducing terminus. Inulin and levan are two basic types of simple fructan, which contain β-(2, 1) and β-(2, 6) fructosyl-fructose linkage, respectively. Fructans not only can serve as soluble dietary fibers for food industry, but also may be biologically converted into high-value products, especially high-fructose syrup and fructo-oligosaccharides. In recent years, much attention has been focused on production of difructose dianhydrides (DFAs) from fructans. DFAs are cyclic disaccharides consisting of two fructose units with formation of two reciprocal glycosidic linkages. They are expected to have promising properties and beneficial effects on human health. DFAs can be produced from fructans by fructan fructotransferases. Inulin fructotransferase (IFTase) (DFA III-forming) and IFTase (DFA I-forming) catalyze the DFA III and DFA I production from inulin, respectively, and levan fructotransferase (LFTase) (DFA IV-forming) catalyzes the production of DFA IV from levan. In this article, the DFA-producing microorganisms are summarized, relevant studies on various DFAs-producing enzymes are reviewed, and especially, the comparisons of the enzymes are presented in detail.

Marine yeast isolation and industrial application

Over the last century, terrestrial yeasts have been widely used in various industries, such as baking, brewing, wine, bioethanol and pharmaceutical protein production. However, only little attention has been given to marine yeasts. Recent research showed that marine yeasts have several unique and promising features over the terrestrial yeasts, for example higher osmosis tolerance, higher special chemical productivity and production of industrial enzymes. These indicate that marine yeasts have great potential to be applied in various industries. This review gathers the most recent techniques used for marine yeast isolation as well as the latest applications of marine yeast in bioethanol, pharmaceutical and enzyme production fields.

Efficient simultaneous saccharification and fermentation of inulin to 2,3-butanediol by thermophilic Bacillus licheniformis ATCC 14580

2,3-Butanediol (2,3-BD) is an important starting material for the manufacture of bulk chemicals. For efficient and large-scale production of 2,3-BD through fermentation, low-cost substrates are required. One such substrate, inulin, is a polydisperse fructan found in a wide variety of plants. In this study, a levanase with high inulinase activity and high pH and temperature stability was identified in Bacillus licheniformis strain ATCC 14580. B. licheniformis strain ATCC 14580 was found to efficiently produce 2,3-BD from fructose at 50°C. Then, the levanase was used for simultaneous saccharification and fermentation (SSF) of inulin to 2,3-BD. A fed-batch SSF yielded 103.0 g/liter 2,3-BD in 30 h, with a high productivity of 3.4 g/liter · h. The results suggest that the SSF process developed with the thermophilic B. licheniformis strain used might be a promising alternative for efficient 2,3-BD production from the favorable substrate inulin.

Direct conversion of inulin into cell lipid by an inulinase-producing yeast Rhodosporidium toruloides 2F5

In this study, an inulinase-producing yeast strain 2F5 of Rhodosporidium toruloides was obtained. It was found that the yeast strain 2F5 could produce higher amount of oil from inulin and larger lipid bodies in its cells than any other yeast strains tested in this study. Under the optimal conditions, 62.14% (w/w) of lipid based on cell dry weight and 15.82g/l of the dry cell mass were produced from 6.0% (w/v) inulin at flask level, leaving 0.92% (w/v) of total sugar in the fermented medium. During 2-l fermentation, 70.36% (w/w) of lipid based on cell dry weight and 15.64g/l of the dry cell mass were produced from 6.0% (w/v) inulin. Over 99.09% of the fatty acids from the yeast strain 2F5 grown on inulin was C16:0, C18:0, C18:1 and C18:2, especially C18:1 (52.2%). The biodiesel prepared using the lipids produced by the yeast strain 2F5 could be burnt well.

Production of an endoinulinase from Aspergillus niger AUMC 9375, by solid state fermentation of agricultural wastes, with purification and characterization of the free and immobilized enzyme

Two different substrates, sunflower (Helianthus annuus L.) tubers and lettuce (Lactuca sativa) roots, were tested. Using a mixture of both wastes resulted in higher production of endoinulinase than either waste alone. Also, ten fungal species grown on these substrates as inexpensive, carbon sources were screened for the best production of endoinulinase activities. Of these, Aspergillus niger AUMC 9375 was the most productive, when grown on the mixture using a 6:1 w/w ratio of sun flower: lettuce, and yielded the highest levels of inulinase at 50% moisture, 30°C, pH 5.0, with seven days of incubation, and with yeast extract as the best nitrogen source. Inulinase was purified to homogeneity by ion-exchange chromatography and gel-filtration giving a 51.11 fold purification. The mixture of sunflower tubers and lettuce roots has potential to be an effective and economical substrate for inulinase production. Inulinase was successfully immobilized with an immobilization yield of 71.28%. After incubation for 2 h at 60°C, the free enzyme activity decreased markedly to 10%, whereas that of the immobilized form decreased only to 87%. A reusability test demonstrated the durability of the immobilized inulinase for 10 cycles and in addition, that it could be stored for 32 days at 4°C. These results indicate that this inulinase, in the immobilized form, is a potential candidate for large-scale production of high purity fructose syrups.

Enhanced expression of endoinulinase from Aspergillus niger by codon optimization in Pichia pastoris and its application in inulooligosaccharide production

In the present study, the endoinulinase gene (EnInu) from Aspergillus niger CICIM F0620 was optimized according to the codon usage of Pichia pastoris and both the native and the optimized gene were expressed in P. pastoris. Use of the optimized gene resulted in the secretion of recombinant endoinulinase activity that reached 1,349 U ml−1, 4.18 times that observed using the native gene. This is the highest endoinulinase activity reported to date. The recombinant enzyme was optimally active at pH 6.0 and 60 °C. Moreover, inulooligosaccharides production from inulin was studied using the recombinant enzyme produced from the optimized gene. After 8 h under optimal conditions, which included 400 g l−1 inulin, an enzyme concentration of 40 U g−1 substrate, 50 °C and pH 6.0, the inulooligosaccharide yield was 91 %. The high substrate concentration and short reaction time described here should reduce production costs distinctly, compared with the conditions used in previous studies. Thus, this study may provide the basis for the industrial use of this recombinant endoinulinase for the production of inulooligosaccharides.

Characterization of inulin hydrolyzing enzyme(s) in commercial glucoamylases and its application in lactic acid production from Jerusalem artichoke tubers (Jat)

A high inulinase activity was found in three commercially available glucoamylase enzymes. Its origin was investigated and two proteins in the commercial glucoamylases were identified as the potential enzymes showing inulinase activity. One of the commercial glucoamylases, GA-L New from Genencor, was used for Jerusalem artichoke tubers (Jat) hydrolysis and a high hydrolysis yield of fructose was obtained. The simultaneous saccharification and lactic acid fermentation (SSF) of Jat was carried out using GA-L New as the inulinase and Pediococcus acidilactici DQ2 as the fermenting strain. A high lactic acid titer, yield, and productivity of 111.5 g/L, 0.46 g/g DM, and 1.55 g/L/h, respectively, were obtained within 72 h. The enzyme cost using the commercial glucoamylase as inulinase was compared to that using the typical inulinase and a large profit margin was identified. The results provided a practical way of Jat application for lactic acid production using cheap commercial glucoamylase enzyme.

Asparagine 42 of the conserved endo-inulinase INU2 motif WMNDPN from Aspergillus ficuum plays a role in activity specificity

Endo-inulinase INU2 from Aspergillus ficuum belongs to glycosidase hydrolase family 32 (GH32) that degrades inulin into fructo oligosaccharides consisting mainly of inulotriose and inulotetraose. The 3D structure of INU2 was recently obtained (Pouyez et al., 2012, Biochimie, 94, 2423–2430). An enlarged cavity compared to exo-inulinase formed by the conserved motif W-M(I)-N-D(E)-P-N-G, the so-called loop 1 and the loop 4, was identified. In the present study we have characterized the importance of 12 residues situated around the enlarged cavity. These residues were mutated by site-directed mutagenesis. Comparative activity analysis was done by plate, spectrophotometric and thin-layer chromatography assay. Most of the mutants were less active than the wild-type enzyme. Most interestingly, mutant N42G differed in the size distribution of the FOS synthesized.

•

Endo-inulinase INU2 degrades inulin into fructo oligosaccharides.

•

12 residues around the catalytic pockets of INU2 enzyme were determined.

•

These residues were mutated to either a G or A residue.

•

The activity has been tested by plate, spectrophotometric and TLC assays.

•

One mutation, N42G, which changes the specificity of activity, has been identified.

Ethanol production from inulin and unsterilized meal of Jerusalem artichoke tubers by Saccharomyces sp. W0 expressing the endo-inulinase gene from Arthrobacter sp

After the endo-inulinase gene from Arthrobacter sp. was ligated the expression vectors pMIDSC31 and pMIRSC31, the endo-inulinase gene was inserted into the chromosomal DNA of Saccharomyces sp. W0. It was found that the inulinase activity of the recombinant yeast D5 in which the endo-inulinase gene was inserted into the delta sequence was higher than that of the recombinant yeast R1 in which the endo-inulinase gene was inserted into 18S rDNA sequence. More ethanol from inulin was produced by the recombinant yeast D5 than by the recombinant yeast R1. But Saccharomyces sp. W0 produced the lowest inulinase activity and concentration of ethanol. During the 3-l fermentation, the recombinant yeast D5 could produce 13.6 ml of ethanol per 100ml of the fermented medium from 30% inulin. The recombinant yeast D5 could actively convert the unsterilized meal of Jerusalem artichoke tubers, yielding 10.1 ml of ethanol per 100ml of the fermented medium.