Effective diffusion coefficients and bioconversion rates of inhibitory compounds in flocs of Saccharomyces cerevisiae

Background: Fermentation strategies for bioethanol production that use flocculating Saccharomyces cerevisiae yeast need to account for the mechanism by which inhibitory compounds, generated in the hydrolysis of lignocellulosic materials, are tolerated and detoxified by a yeast floc. Results: Diffusion coefficients and first-order kinetic bioconversion rate coefficients were measured for three fermentation inhibitory compounds (furfural, hydroxymethylfurfural, and vanillin) in self-aggregated flocs of S. cerevisiae NRRL Y-265. Thièle-type moduli and internal effectiveness factors were obtained by simulating a simple steady-state spherical floc model. Conclusions: The obtained values for the Thiéle moduli and internal effectiveness factors showed that the bioconversion rate of the inhibitory compounds is the dominant phenomenon over mass transfer inside the flocs.

Effects of Acorus tatarinowii Schott and its active component -5- hydroxymethylfurfural on ERK/CREB signal in hippocampus of exercise-induced fatigue rats / 中国应用生理学杂志

OBJECTIVE@#To investigate the effects of Acorus tatarinowii Schott and its active component 5- hydroxymethyl furfural (HMF) on learning and memory and ERK/CREB signal in hippocampus of rats with exercise-induced fatigue.@*METHODS@#SD rats were randomly divided into normal group (A), exercise group (B), exercise + HMF low, middle and high dose treatment group (C, D, E), exercise + acorus tatarinowii Schott low, middle and high dose treatment group (F, G, H), with ten rats in each group. The rats in group C, D and E were treated with HMF at the doses of 0.10, 1.00 and 3.00 mg. kg by ig. The rats in group F, G and H were treated with the extracts of Acorus tatarinowii Schott at the doses of 0.12, 1.20 and 4.80 g. kg by ig. Learning and memory of rats were tested by the method of water maze experiment, and the expression levels of p-ERK1/2 and p-CREB protein in hippocampus of rats were tested by the method of Western blot in the end of the experiment.@*RESULTS@#The escape latencies of E and H groups were lower than those of groups B, C, D, F and G; and the numbers of plateau crossing were more than those of groups B, C, D, F and G and the expression levels of p-ERK1/2, p-CREB protein were higher than those of groups B, C, D, F and G , respectively(P ＜ 0.01). There was no significant difference in the above indexes among groups A, E and H(P＞0.05) except that the expression levels of p-ERK2 protein in group E were lower than those in group A and H (P＜0.05).@*CONCLUSION@#Acorus tatarinowii and its active component- HMF can improve the learning and memory of rats with exercise-induced fatigue, and the mechanism is related to the up-regulation of ERK / CREB signal in hippocampus of rats with exercise-induced fatigue.

Qualitative and quantitative analysis on non-triterpenoids in Ligustri Lucidi Fructus / 中国中药杂志

In order to improve the quality control level of Ligustri Lucidi Fructus(LLF) and to explore the changes of chemical components after processing,the HPLC method for fingerprint and simultaneous determination of the major polar components in LLF were established. The octadecylsilane bonded silica gel was used as the stationary phase,with acetonitrile as the mobile phase A and0. 2% formic acid as the mobile phase B in a gradient elution procedure at a flow rate of 1. 0 m L·min-1. The detection wavelength was set at 280 nm and the column temperature was 25 ℃. There were 22 common peaks,20 of which were selected from the fingerprint of LLF and its wine-steamed product,respectively,and 14 chromatographic peaks were identified with reference substances. With the same chromatographic conditions,seven components were quantitatively analyzed and the results of system adaptability and methodology investigation all met the requirements of content determination. Compared with the crude LLF,the content of 5-hydroxymethyl furfural and salidroside significantly increased in wine-steamed LLF,while the contents of iridoid glycosides generally decreased. The method provided a basis for quality control of LLF and its processed products as well as the related preparations.

Xylitol production and furfural consumption by a wild type Geotrichum sp

Background: Xylitol is a five carbons polyol with promising medical applications. It can be obtained from chemical D-xylose reduction or by microbial fermentation of Sugarcane Bagasse Hemicellulosic Hydrolysate. For this last process, some microbial inhibitors, as furfural, constitute severe bottleneck. In this case, the use of strains able to produce xylitol simultaneously to furfural neutralization is an interesting alternative. A wild-type strain of Geotrichum sp. was detected with this ability, and its performance in xylitol production and furfural consumption was evaluated. Furthermore, were analyzed its degradation products. Results: Geotrichum sp. produced xylitol from D-xylose fermentation with a yield of 0.44 g-g-1. Furfural was fully consumed in fermentation assay and when provided in the medium until concentration of 6 g-L-1. The furfural degradation product is not an identified molecule, presenting a molecular weight of 161 g-mol-1, an uncommon feature for the microbial metabolism of this product. Conclusion: This strain presents most remarkable potential in performing furfural consumption simultaneous to xylitol production. Subsequent efforts must be employed to establish bioprocess to simultaneous detoxification and xylitol production by Geotrichum sp.

5-Hydroxymethylfurfural protects against ER stress-induced apoptosis in GalN/TNF-α-injured L02 hepatocytes through regulating the PERK-eIF2α signaling pathway / 中国天然药物

5-Hydroxymethylfurfural (5-HMF), a water-soluble compound extracted from wine-processed Fructus corni, is a novel hepatic protectant for treating acute liver injury. The present study was designed to investigate the protective effect of 5-HMF in human L02 hepatocytes injured by D-galactosamine (GalN) and tumor necrosis factor-α (TNF-α) in vitro and to explore the underlying mechanisms of action. Our results showed that 5-HMF caused significant increase in the viability of L02 cells injured by GalN/TNF-α, in accordance with a dose-dependent decrease in apoptotic cell death confirmed by morphological and flow cytometric analyses. Based on immunofluorescence and Western blot assays, we found that GalN/TNF-α induced ER stress in the cells, as indicated by the disturbance of intracellular Ca(2+) concentration, the activation of protein kinase RNA (PKR)-like ER kinase (PERK), phosphorylation of eukaryotic initiation factor 2 alpha (eIF2α), and expression of ATF4 and CHOP proteins, which was reversed by 5-HMF pre-treatment in a dose-dependent manner. The anti-apoptotic effect of 5-HMF was further evidenced by balancing the expression of Bcl-2 family members. In addition, the knockdown of PERK suppressed the expression of phospho-PERK, phospho-eIF2α, ATF4, and CHOP, resulting in a significant decrease in cell apoptosis after the treatment with GalN/TNF-α. 5-HMF could enhance the effects of PERK knockdown, protecting the cells against the GalN/TNF-α insult. In conclusion, these findings demonstrate that 5-HMF can effectively protect GalN/TNF-α-injured L02 hepatocytes against ER stress-induced apoptosis through the regulation of the PERK-eIF2α signaling pathway, suggesting that it is a possible candidate for liver disease therapy.

Cause and control of Radix Ophiopogonis browning during storage / 中国天然药物

In the storage of Radix Ophiopogonis, browning often happens to cause potential risk with regard to safety. Previously few reports investigate the browning of Radix Ophiopogonis. In this research, the causes and mechanisms of the browning of Radix Ophiopogonis were preliminarily elucidated. Content determination by high-performance liquid chromatography (HPLC) and spectrophotometry, enzyme activity determination by colorimetry, and morphological observation by electron microscopy were performed in the present study. Uniform design and three-dimensional response surfaces were applied to investigate the relationship between browning and storage factors. The cortex cell wall of browned Radix Ophiopogonis was ruptured. Compared with the normal Radix Ophiopogonis, cellulase and polyphenol oxidase enzymes were activated, the levels of 5-hydroxymethylfurfural (5-HMF), total sugars, and reducing sugars were increased, while the levels of polysaccharides and methylophiopogonanone A were decreased in browned Radix Ophiopogonis. The relationship between the storage factors and degree of browning (Y) could be described by following correlation equation: Y = - 0.625 4 + 0.020 84 × X3 + 0.001 514 × X1 × X2 - 0.000 964 4 × X2 × X3. Accompanied with browning under storage conditions, the chemical composition of Radix Ophiopogonis was altered. Following the activation of cellulase, the rupture of the cortex cell wall and the outflow of cell substances flowed out, which caused the Radix Ophiopogonis tissue to become soft and sticky. The main causes of the browning were the production of 5-HMF, the activation of polyphenol oxidase, Maillard reactions and enzymatic browning. Browning could be effectively prevented when the air relative humidity (HR), temperature, and moisture content were under 25% RH, 12 °C and 18%, respectively.

High titer ethanol production from an atmospheric glycerol autocatalytic organosolv pretreated wheat straw / 生物工程学报

The expensive production of bioethanol is because it has not yet reached the 'THREE-HIGH' (High-titer, high-conversion and high-productivity) technical levels of starchy ethanol production. To cope with it, it is necessary to implement a high-gravity mash bioethanol production (HMBP), in which sugar hydrolysates are thick and fermentation-inhibitive compounds are negligible. In this work, HMBP from an atmospheric glycerol autocatalytic organosolv pretreated wheat straw was carried out with different fermentation strategies. Under an optimized condition (15% substrate concentration, 10 g/L (NH4)2SO4, 30 FPU/g dry matter, 10% (V/V) inoculum ratio), HMBP was at 31.2 g/L with a shaking simultaneous saccharification and fermentation (SSF) at 37 degrees C for 72 h, and achieved with a conversion of 73% and a productivity of 0.43 g/(L x h). Further by a semi-SFF with pre-hydrolysis time of 24 h, HMBP reached 33.7 g/L, the conversion and productivity of which was 79% and 0.47 g/(L x h), respectively. During the SSF and semi-SSF, more than 90% of the cellulose in both substrates were hydrolyzed into fermentable sugars. Finally, a fed-batch semi-SFF was developed with an initial substrate concentration of 15%, in which dried substrate (= the weight of the initial substrate) was divided into three portions and added into the conical flask once each 8 h during the first 24 h. HMBP achieved at 51.2 g/L for 72 h with a high productivity of 0.71 g/(L x h) while a low cellulose conversion of 62%. Interestingly, the fermentation inhibitive compound was mainly acetic acid, less than 3.0 g/L, and there were no other inhibitors detected, commonly furfural and hydroxymethyl furfural existing in the slurry. The data indicate that the lignocellulosic substrate subjected to the atmospheric glycerol autocatalytic organosolv pretreatment is very applicable for HMBP. The fed-batch semi-SFF is effective and desirable to realize an HMBP.

Effects of furfural on the growth and lipid production of oleaginous yeast Rhodotorula glutinis / 生物工程学报

In order to illustrate the effects of furfural, one of the most common inhibitory compounds in lignocellulosic hydrolysate, on oleaginous yeast Rhodotorula glutinis, we investigated the effects of different concentrations of furfural (0.1, 0.4, 0.6 and 1.5 g/L) on the biomass and lipid production of R. glutinis, as well as the effects of 1.0 g/L furfural on the utilization of glucose and xylose. Results showed that: when the furfural concentration reached 1.5 g/L, the lag phrase time was extended to 96 h, and the residual glucose was up to 17.7 g/L, with maximum biomass of only 6.6 g/L, which accounted for 47% of that in the basic medium (furfural-free), and the corresponding lipid content was reduced about 50%. Furfural showed lighter inhibitory degree on R. glutinis when xylose acted as the carbon source than glucose was the carbon source; more C18 fatty acids or unsaturated C18 fatty acids were generated in the presence of furfural.

Adsorption mechanism of furfural onto modified rice husk charcoals / 生物工程学报

To evaluate the absorptive characteristics of furfural onto biomass charcoals derived from rice husk pyrolysis, we studied the information of the structure and surface chemistry properties of the rice husk charcoals modified by thermal treatment under nitrogen and carbon dioxide flow and adsorption mechanism of furfural. The modified samples are labeled as RH-N2 and RH-CO2. Fresh rice husk charcoal sample (RH-450) and modified samples were characterized by elemental analysis, nitrogen adsorption-desorption isotherms, Fourier-transform infrared spectroscopy and Boehm titration. The results show that fresh rice husk charcoal obtained at 450 degrees C had a large number of organic groups on its surface and poor pore structure. After the modification under nitrogen and carbon dioxide flow, oxygenic organics in rice husk charcoals decompose further, leading to the reduction of acidic functional groups on charcoals surface, and the increase of the pyrone structures of the basic groups. Meanwhile, pore structure was improved significantly and the surface area was increased, especially for the micropores. This resulted in the increase of π-π dispersion between the surfaces of rice husk charcoals and furfural molecular. With making comprehensive consideration of π-π dispersion and pore structure, the best removal efficiency of furfural was obtained by rice husk charcoal modified under carbon dioxide flow.

Biomass fast pyrolysis for bio-oil production in a fluidized bed reactor under hot flue atmosphere / 生物工程学报

Fast pyrolysis experiments of corn stalk were performed to investigate the optimal pyrolysis conditions of temperature and bed material for maximum bio-oil production under flue gas atmosphere. Under the optimized pyrolysis conditions, furfural residue, xylose residue and kelp seaweed were pyrolyzed to examine their yield distributions of products, and the physical characteristics of bio-oil were studied. The best flow rate of the flue gas at selected temperature is obtained, and the pyrolysis temperature at 500 degrees C and dolomite as bed material could give a maximum bio-oil yield. The highest bio-oil yield of 43.3% (W/W) was achieved from corn stalk under the optimal conditions. Two main fractions were recovered from the stratified bio-oils: light oils and heavy oils. The physical properties of heavy oils from all feedstocks varied little. The calorific values of heavy oils were much higher than that of light oils. The pyrolysis gas could be used as a gaseous fuel due to a relatively high calorific value of 6.5-8.5 MJ/m3.

Comparison of chemical composition between raw and vinegar-baked Paeoniae Radix Alba using NMR based metabolomic approach / 药学学报

To compare the chemical change of Paeoniae Radix Alba (PRA) after vinegar-baking processing, as well as the effect of vinegar types exerted on the processing, 1H NMR-based metabolomic approach combined with multivariate statistical analysis was used to investigate the different metabolites between the raw and two vinegar-baked PRA. More than thirty metabolites were identified in the 1H NMR spectrum of PRA, and the multivariate statistical analysis showed that raw and two vinegar-baked PRA could be separated obviously. After vinegar-baking, the contents of isoleucine, lactate, alanine, arginine, albiflorin, and 5-hydroxymethyl furfural (5-HMF) elevated, while those of sucrose, paeoniflorin and its analogues (calculated by benzoate) decreased. The chemical compositions of two vinegar-baked PRA were also different. Shanxi vinegar- baked PRA showed higher levels of leucine, isoleucine, valine, and albiflorin, while rice vinegar-baked PRA contained more sucrose and paeoniflorin's analogues (calculated by benzoate). And the chemical changes in Shanxi vinegar-baked PRA were greater than those of rice vinegar-baked PRA. The results revealed the chemical differences between raw and vinegar-baked PRA, as well as the influence of vinegar type on processing, in a holistic manner, the results obtained suggested that the correlations between the chemical change and the drug action after processing, as well as the vinegar type used in processing, should be further studied.

Chemical constituents from whole plants of Aconitum tanguticum (III) / 中国中药杂志

Nineteen compounds were isolated from the whole plants of Aconitum tanguticum by various of chromatographic techniques and their structures were determined through spectral analysis (1D, 2D-NMR and MS) and comparison with the literature data. These compounds were identified as 5-hydroxymethy furfural (1), 5-acetoxymethyl furfural (2), pyrrolezanthine [5-hydroxymethyl-1-[2-(4-hydroxyphenyl) -ethyl] -1H-pyrrole-2-carbaldehyde] (3), lichiol B (4), phthalic acid dibutyl ester (5), 3, 4-dihydroxy phenylethanol (6), 3, 4-dihydroxy phenylethanol glucoside (7), salidroside (8), p-hydroxy phenylethanol (9), p-hydroxybenzoie acid glucoside (10), p-hydroxybenzoic acid (11), gastrodin (12), 1-(3, 4-dimethoxyphenyl) -1, 2-ethanediol (13), p-hydroxy benzaldehyde (14), p-hydroxy acetophenone (15), 3, 4-dihydroxy phenyl ethyl acetate (16), syringic aldehyde (17), ethyl beta-D-fructopyranoside (18), and p-hydroxybenzoic acid methyl ester (19). Compounds 3 and 4 were isolated from the Ranunculaceae family for the first time, and compounds 2, 6 and 9-19 were isolated from the Aconitum genus for the first time, and compounds 1 and 5 were isolated from the species for the first time.

Effect of byproducts in lignocellulose hydrolysates on ethanol fermentation by Issatchenkia orientalis / 生物工程学报

Byproducts in lignocellulose hydrolysates, namely sodium formate (1 to 5 g/L), sodium acetic (2.5 to 8.0 g/L), furfural (0.2-2 g/L), 5-hydroxymethylfurfural (5-HMF, 1 to 1.0 g/L) or vanillin (0.5 to 2 g/L) were used to evaluate their effects on ethanol fermentation by Issatchenkia orientalis HN-1 using single factor test and the response surface central composite experiment. Results showed that most of the byproducts had no obvious inhibition on the production of ethanol, except for the addition of 2 g/L vanillin or 1 g/L of 5-HMF, which reduced the ethanol production by 20.38% and 11.2%, respectively. However, high concentration of some byproducts in lignocellulose hydrolysates, such as sodium formate (1 to 5 g/L), sodium acetic (2.5 to 8.0 g/L), furfural (0.2 to 2 g/L) and vanillin (0.5 to 2 g/L) inhibited the growth of I. orientalis HN-1 significantly. Compared with the control, the dry cell weight of I. orientalis HN-1 decreased by 25.04% to 37.02%, 28.83% to 43.82%, 20.06% to 37.60% and 26.39% to 52.64%, respectively, when the above components were added into the fermentation broth and the fermentation lasted for 36 h. No significant interaction effect of the various inhibitors (sodium formate, sodium acetic, furfural and vanillin) except for vanillin single factor on the ethanol production was observed based on the central composite experiments. The concentrations of byproducts in most lignocellulose hydrolysates were below the initial inhibition concentration on ethanol production by Issatchenkia orientalis HN-1, which indicated that Issatchenkia orientalis HN-1 can be used for ethanol production from lignocellulose hydrolysates.

Effects of 5-hydroxymethyl furfural extracted from Rehmannia glutinosa Libosch on the expression of signaling molecules relevant to learning and memory among hippocampal neurons exposed to high concentration of corticosterone / 中国结合医学杂志

<p><b>OBJECTIVE</b>To determine the effects of 5-hydroxymethyl furfural (5-HMF), an extract of Rehmannia glutinosa Libosch, on several down-regulated signaling molecules involved in learning and memory in hippocampal neurons.</p><p><b>METHODS</b>After cultured for 7 days, primary hippocampal neurons were divided into 5 groups: normal, corticosterone model, RU38486, 5-HMF, and donepezil group. Neuron survival rates were calculated 24 h later using SYTO13-PI double-fluorescence staining and an 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. β-galactosidase activity was also assayed. Protein expressed by the glucocorticoid receptor (GCR), brainderived neurotrophic factor (BDNF), and N-methyl-D-aspartate receptor 2B (NR2B), as well as phosphorylationcyclic adenosine monophosphate (cAMP) response element binding protein (p-CREB), phosphorylation-extracellular signal-regulated kinase (p-ERK), and phosphorylation-synapsin (p-synapsin) were quantified with Western blot.</p><p><b>RESULTS</b>Hippocampal neuron survival rates and the above-mentioned proteins were dramatically decreased (P<0.05), β-galactosidase activity was significantly increased in the model group. but the effect was reversed by 5-HMF, RU38486, and to a lesser extent by donepezil (P<0.05).</p><p><b>CONCLUSION</b>5-HMF extracts from the Chinese herb Rehmannia glutinosa Libosch could protect hippocampal neurons from glucocorticoid injury and from down-regulated signaling molecules in the GCR-BDNF-NR2B-p-ERK-p-CREB-p-synapsin signal transduction pathway.</p>

Preliminary study of odor change mechanism in Crataegi fructus stir-fried process based on correlation analysis / 中国中药杂志

In order to investigate the mechanism, the correlation between the odor change in Crataegi Fructus stir-fried process and 5-HMF were studied. Required samples were retrieved from Crataegi Fructus stir-fried process. Statistical quality control (SQC) was used to analyze the response values acquired by the electronic nose. At the same time, the content of 5-HMF was detected by high performance liquid chromatography (HPLC). Correlation analysis was used to analyze the relationship between the above two. Experimental results showed that SQC model established by response values of all samples could show the change law of odor in Crataegi Fructus stir-fried process and changes of 5-HMF content was dropped after the first increase. Correlation analysis showed that the odor change in Crataegi Fructus stir-fried process and 5-HMF were significantly correlated (P < 0.05). Sugar degradation reaction and the Maillard reaction may be one of the mechanisms of the odor change in Crataegi Fructus stir-fried process.

Rapid screening and quality evaluation for the harmful substance 5-hydroxymethyl furfural in commercially available traditional Chinese medicine injection using LC-MS/MS method / 药学学报

To screen the harmful substance 5-hydroxymethyl furfural content in commercially available traditional Chinese medicine injection which are commonly used, and to preliminarily evaluate the quality of these injections, 5-hydroxymethyl furfural was taken as an index. The contents of 5-hydroxymethyl furfural in 56 samples which consist of 23 kinds of traditional Chinese medicine injections and glucose injection were determined using LC-MS/MS, and 5-hydroxymethyl furfural was detected in 52 of these samples. The minimal content was 0.0038 microg x L(-1) and the maximum content was 1420 microg x mL(-1). The contents of 5-hydroxymethyl furfural were significantly different in traditional Chinese medicine injection which came from different kinds, manufacturers or batches. The results showed the quality difference of commercially available traditional Chinese medicine injection is significant taking 5-hydroxymethyl furfural content as assessment index. More attention should be paid to the safety of 5-hydroxymethyl furfural in traditional Chinese medicine injection, and unified limitation standard should be set to improve medication safety of traditional Chinese medicine injection.

Effects of furfural and 5-hydroxymethylfurfural on succinic acid production by Escherichia coli / 生物工程学报

Succinic acid production by fermentation from biomass, especially the lignocellulosic hydrolysate, is an alternative to chemical synthesis. Many studies report the inhibition of cell growth and succinic acid production from lignocellulosic hydrolysate, hardly is known about the actual kinetic and mechanism of the inhibition of individual factors. In this study, we studied inhibition effects of furfurals and 5-hydroxymethylfurfural (5-HMF) on cell growth and succinic acid production of engineered E. coli. Cell growth and succinic acid titer were severely inhibited by furfural and HMF with both concentrations higher than 0.8 g/L. Cell growth was totally inhibited when the concentration of furfural was above 6.4 g/L, or the concentration of HMF was above 12.8 g/L. At the concentration of maximum toleration, which was 3.2 g/L, furfural decreased the cell mass by 77.8% and the succinic acid titer by 36.1%. HMF decreased the cell mass by 13.6% and the succinic acid titer by 18.3%. Activity measurements of key enzymes revealed that phosphoenolpyruvate carboxylase, malate dehydrogenase, fumarate reductase all were inhibited by furfural and HMF. This study gave a quantitative view to the succinic acid production under the inhibition of lignocellulose degradation products and will help overcome the difficulties of the lignocellulosic hydrolysate fermentation.

Chemical constituents from the roots of Angelica polymorpha Maxim / 药学学报

Angelica polymorpha Maxim. is a plant of the Angelica genus (Umbelliferae). The root and stem of this plant is a folk medicine known to have the actions of relieving rheumatism and cold and subsiding swelling and pains. To investigate the chemical constituents in the root of A. polymorpha Maxim., seven compounds were isolated from an 80% ethanol extract by column chromatography. Their structures were elucidated according to the spectroscopic analysis. Compound 1 is a new sesquiterpene, named as bisabolactone. Its absolute configuration was determined by 1D NOESY and CD analysis. The others were identified as 5-hydroxymethylfurfural (2), hycandinic acid ester 1 (3), ferulic acid (4), isooxypeucedanin (5), noreugenin (6) and cimifugin (7). Compound 2 and 3 were isolated from this genus for the first time and compound 4 was isolated from this plant for the first time.

Effect of acetic acid, furfural and 5-hydroxymethylfurfural on production of 2,3-butanediol by Klebsiella oxytoca / 生物工程学报

To get the tolerability and consumption of Klebsiella oxytoca on major inhibitors in lignocelluloses hydrolysate, we studied the effect of acetic acid, furfural and 5-hydroxymethylfurfural on production of 2,3-butanediol by Klebsiella oxytoca. The metabolites of furfural and 5-hydroxymethylfurfural were measured. The results show that when acetic acid, furfural and 5-hydroxymethylfurfural was individually added, tolerance threshold for Klebsiella oxytoca was 30 g/L, 4 g/L and 5 g/L, respectively. Acetic acid was likely used as substrate to produce 2,3-butanediol. The yield of 2,3-butanediol increased when acetic acid concentration was lower than 30 g/L. In the fermentation, more than 70% 5-hydroxymethylfurfural was converted to 2,5-furandimethanol. All furfural and the rest of 5-hydroxymethylfurfural were metabolized by Klebsiella oxytoca. It showed that in the detoxification process of 2,3-butanediol production using lignocelluloses hydrolysate, furfural should be given priority to remove and a certain concentration of acetic acid is not need to removal.

Furfural degradation by filamentous fungus Amorphotheca resinae ZN1 / 生物工程学报

Some degradation products from lignocellulose pretreatment strongly inhibit the activities of cellulolytic enzymes and ethanol fermentation strains, thus the efficient removal of the inhibitor substances ("detoxification") is the inevitable step for the biotransformation processes. In this study, the biological detoxification of furfural by a newly isolated fungus, Amorphotheca resinae ZN1, was studied and the metabolic pathways of furfural degradation was analyzed. The metabolic pathway of furfural degradation in A. resinae ZN1 was described as follows: first, furfural was quickly converted into the low toxic furfuryl alcohol; then the furfuryl alcohol was gradually converted into furfural again but under the low concentration under aerobic condition, which was not lethal to the growth of the fungi; furfural continued to be oxidized to furoic acid by A. resinae ZN1. It is likely that furoic acid was further degraded in the TCA cycle to complete the biological degradation of furfural. The present study provided the important experimental basis for speeding up the biodetoxification of furfural by A. resinae ZN1 and the rate-limiting step in the lignocellulose biotransformation to ethanol.