Applied Biochemistry and Biotechnology (v.166, #7)

Oil Palm Empty Fruit Bunch as Alternative Substrate for Acetone–Butanol–Ethanol Production by Clostridium butyricum EB6 by Mohamad Faizal Ibrahim; Suraini Abd-Aziz; Mohamad Nafis Abdul Razak; Lai Yee Phang; Mohd Ali Hassan (1615-1625).
Acetone–butanol–ethanol (ABE) production from renewable resources has been widely reported. In this study, Clostridium butyricum EB6 was employed for ABE fermentation using fermentable sugar derived from treated oil palm empty fruit bunch (OPEFB). A higher amount of ABE (2.61 g/l) was produced in a fermentation using treated OPEFB as the substrate when compared to a glucose based medium that produced 0.24 g/l at pH 5.5. ABE production was increased to 3.47 g/l with a yield of 0.24 g/g at pH 6.0. The fermentation using limited nitrogen concentration of 3 g/l improved the ABE yield by 64%. The study showed that OPEFB has the potential to be applied for renewable ABE production by C. butyricum EB6.
Keywords: Clostridium butyricum ; Acetone butanol ethanol (ABE); Oil palm empty fruit bunch (OPEFB); Anaerobic fermentation; Biomass

Ubiquitous Amyloids by Wojciech Pulawski; Umesh Ghoshdastider; Vincenza Andrisano; Slawomir Filipek (1626-1643).
The common view of amyloids and prion proteins is that they are associated with many currently incurable diseases and present a great danger to an organism. This danger comes from the fact that not only prion proteins, but also the infectious form(s) of amyloids, as it has been shown recently, are able to transmit the disease. On the other hand, organisms take advantage of the strength and durability of specific forms of amyloids. Such forms do not spread any disease. Also, in nanotechnology there is a constantly growing need to employ amyloid fibrils in many industrial applications. With increasing knowledge about amyloids and prion proteins we are aware that the amyloidal state is inherent to any protein, making the problem of amyloid formation a central one in aging-related diseases. However, the “good” amyloids can be beneficial and even necessary for our health. Furthermore, because of their mechanical properties, the amyloids are of great interest to engineers.
Keywords: Amyloids; Prions; Fibrils; Amylome; Amyloidogenic segments; Aging diseases

In Vitro Production of Plant Peroxidases—A Review by Nuria González-Rábade; María del Carmen Oliver-Salvador; Edgar Salgado-Manjarrez; Jesús Agustín Badillo-Corona (1644-1660).
In the latest two decades, the interest received by plant enzymes has increased significantly. Plant enzymes such as peroxidases are widely used in medicine as diagnostic tools and in the bioremediation and biobleaching industries, among others. Traditionally, these enzymes have been obtained from a natural source, a process that is sometimes laborious and affected by weather conditions and low yields. To overcome this hurdle, some efforts have been made to establish plant cell cultures in vitro to use the system as a continuous source of plant enzymes. The focus of this review will be the production of plant peroxidases in vitro, including novel approaches such as the use of bioreactors and genetically transformed tissues to enhance the yield of desired enzymes.
Keywords: Plant enzymes; Peroxidases; In vitro

Influence of Exogenous CO2 on Biomass and Lipid Accumulation of Microalgae Auxenochlorella protothecoides Cultivated in Concentrated Municipal Wastewater by Bing Hu; Min Min; Wenguang Zhou; Yecong Li; Michael Mohr; Yanling Cheng; Hanwu Lei; Yuhuan Liu; Xiangyang Lin; Paul Chen; Roger Ruan (1661-1673).
The effects of exogenous CO2 on the growth and lipid accumulation of a local screened facultative heterotrophic microalgae strain Auxenochlorella protothecoides (UMN280) as well as nutrient removal from concentrated municipal wastewater stream (centrate) were examined in this study. A 12-day batch experiment was conducted with CO2 aeration at three levels, namely, 0%, 1%, and 5% (v/v) CO2 mixed with air, under light intensity of 60 μmol/(m2 @@s). A two-stage growth pattern was observed. The first stage (first–fifth day) was dominated by heterotrophic growth in which organic carbon was the main carbon source. The second stage (6th–12th day) was dominated by autotrophic growth in which exogenous CO2 had a positive effect on algal biomass accumulation. The addition of 5% CO2 was better than that of 1% CO2 on the biomass and lipid production. The uptakes of nutrients were similar between injection and no injection of CO2, except on phosphorus removal which was affected by the acidification of CO2.
Keywords: Microalgae; Mixotrophic growth; Concentrated municipal wastewater; Nutrient removal; CO2

An Protocol for Genetic Transformation of Catharanthus roseus by Agrobacterium rhizogenes A4 by Mei-Liang Zhou; Xue-Mei Zhu; Ji-Rong Shao; Yan-Min Wu; Yi-Xiong Tang (1674-1684).
Catharanthus roseus (L.) G. Don is a plant species known for its production of a variety of terpenoid indole alkaloids, many of which have pharmacological activities. Catharanthine can be chemically coupled to the abundant leaf alkaloid vindoline to form the valuable anticancer drug vinblastine. To study and extract catharanthine and other metabolites from C. roseus, a technique was developed for producing hairy root cultures. In this study, the Agrobacterium rhizogenes A4 was induced in the hairy roots from leaf explants, and the concentration of antibiotics (100 mg/L kanamycin) was elucidated for selection after transformation. The polymerase chain reaction amplification of rol genes results revealed that transgenic hairy roots contained rol genes from the root induced (Ri)-plasmid. Catharanthine from C. roseus hairy roots was separated and analyzed using high-performance liquid chromatography. Over-expression of CrOrca3 (octadecanoid-responsive Catharanthus AP2/ERF domain), and cytohistochemical staining methods were used to validate transgenic hairy roots from C. roseus. Hairy root culture of C. roseus is a valuable approach for future efforts in the metabolic engineering of terpenoid indole alkaloids in plants.
Keywords: Agropine synthase; Alkaloid; Hairy root; Madagascar periwinkle; Metabolic engineering; Tissue culture

Extracellular Polymeric Substances (EPS) from Aerobic Granular Sludges: Extraction, Fractionation, and Anionic Properties by Cédric Caudan; Ahlem Filali; Dominique Lefebvre; Mathieu Spérandio; Elisabeth Girbal-Neuhauser (1685-1702).
A multi-method protocol previously proposed for the extraction of extracellular polymeric substances (EPS) from flocculated sludges was investigated on dense aerobic granules. The protocol combines mechanical disruption by sonication and chemical extraction using the Tween detergent and the cation chelator, EDTA. Polysaccharides were mainly recovered during the first sonication step while proteins were recovered all along the extractive procedure with a high prevalence in the EDTA step. These data confirmed the interest of the multi-method protocol for harvesting a diversified pool of EPS from dense granules and for fractionation of the polymers according to their physicochemical properties. In addition, the high extractability of proteins with EDTA confers a specific behavior of the aerobic granules towards the multi-method extraction protocol, supporting the idea that proteins are associated in the granule matrix through ionic interactions involving divalent cations. Analysis of the extracted EPS by anionic exchange chromatography confirmed the presence of highly anionic proteins that were specifically detected in the extracts obtained from granules. One important question is now to investigate whether these highly anionic proteins are involved in the aggregation and densification process and if their presence is related to the cohesive properties of these particles.
Keywords: Aerobic granules; Extracellular polymeric substances; Multi-method extraction; Anionic polymers; Divalent cation bridging

Expression and Structure/Function Relationships of Human Defensin 5 by Nava Chapnik; Anat Levit; Masha Y. Niv; Oren Froy (1703-1710).
The innate immunity utilizes a battery of broad-spectrum antibacterial cationic polypeptides (3–5 kDa), among them defensins. In humans, defensins are the first line of defense against pathogens and their expression has been implicated in several diseases. The antibacterial activity of defensins is generally ascribed to their overall positive charge, which enables them to disrupt bacterial membrane integrity and function, but their active surface has not been fully elucidated. To perform structural and functional assays, an efficient, high-yield, easy-to-use expression and purification system must be established. Up to now, most efforts to obtain larger quantities of active recombinant defensins have been only moderately successful. Herein, we report the establishment of an efficient, high-yield expression and purification system for human defensin 5 (HD-5). Using site-directed mutagenesis, we pinpoint several arginine residues and Y27 as important for HD-5 antibacterial activity. Our expression and purification system can be harnessed for structure/activity relationship studies of defensins in particular and small polypeptides in general.
Keywords: HD-5; Defensins; Expression; Site-directed mutagenesis

Preparation of Magnetic Nanoparticles and Their Use for Immobilization of C-Terminally Lysine-Tagged Bacillus sp. TS-23 α-Amylase by Yan-Hung Chen; Meng-Chun Chi; Tzu-Fan Wang; Jui-Chang Chen; Long-Liu Lin (1711-1722).
The aim of this investigation was to synthesize the adipic acid-modified magnetic nanoparticles for the efficient immobilization of C-terminally lysine-tagged α-amylase (BACΔNC-Lys7) from thermophilic Bacillus sp. strain TS-23. The carboxylated magnetic nanoparticles were prepared by the simple co-precipitation of Fe3+/Fe2+ in aqueous medium and then subsequently modified with adipic acid. Transmission electron microscopy micrographs showed that the carboxylated magnetic nanoparticles remained discrete and had no significant change in size after the binding of BACΔNC-Lys7. Free enzyme was active in the temperature range of 45–70 °C and had an optimum of 60 °C, whereas the thermal stability of BACΔNC-Lys7 was improved as a result of immobilization. The immobilized BACΔNC-Lys7 could be recycled 20 times without a significant loss of the amylase activity and had a better stability during storage with respect to free enzyme. Taken together, the magnetic nanoparticles coated with this functional moiety can be a versatile platform for the effective manipulation of various kinds of engineered proteins.
Keywords: Magnetic nanoparticles; Lysine-tagged α-amylase; Immobilization; Stability; Reusability

A Temperature and Salt-Tolerant l-Glutaminase from Gangotri Region of Uttarakhand Himalaya: Enzyme Purification and Characterization by Lokendra Kumar; Balvinder Singh; Dilip Kumar Adhikari; Joydeep Mukherjee; Debashish Ghosh (1723-1735).
Purification and characterization of halotolerant, thermostable alkaline l-glutaminase from a Bacillus sp. LKG-01 (MTCC 10401), isolated from Gangotri region of Uttarakhand Himalaya, is being reported in this paper. Enzyme has been purified 49-fold from cell-free extract with 25% recovery (specific activity 584.2 U/mg protein) by (NH4)2SO4 precipitation followed by anion exchange chromatography and gel filtration. Enzyme has a molecular weight of 66 kDa. l-Glutaminase is most active at pH 11.0 and stable in the pH range 8.0–11.0. Temperature optimum is 70 °C and is completely stable after 3 h pre-incubation at 50 °C. Enzyme reflects more enhanced activity with 1–20% (w/v) NaCl, which is further reduced to 80% when NaCl concentration was increased up to 25%. l-Glutaminase is almost active with K+, Zn2+, and Ni2+ ions and K m and V max values of 240 μM and 277.77 ± 1.1 U/mg proteins, respectively. Higher specific activity, purification fold, better halo-tolerance, and thermostability would make this enzyme more attractive for food fermentation with respect to other soil microbe derived l-glutaminase reported so far.
Keywords: l-Glutaminase; NaCl; Thermostability; Alkaline pH

Lysozyme Immobilized on Micro-Sized Magnetic Particles: Kinetic Parameters at Wine pH by Katia Liburdi; Raffaello Straniero; Ilaria Benucci; Anna Maria Vittoria Garzillo; Marco Esti (1736-1746).
In order to use lysozyme as an anti-microbial agent during the winemaking process, hen egg-white lysozyme (LYZ) was covalently immobilized on two different micro-size magnetic particles (tosyl-activated and carboxylated, TSA and CA, respectively). A cell suspension of Oenococcus oeni, an oenological strain involved in the winemaking process, was utilized as LYZ substrate. Both a kinetic study and a study of the stability of free and immobilized LYZ were performed in McIlvane buffer at pH 3.2, that is the average minimum pH value in wine. The activity and kinetic parameters measured for the free LYZ at pH 3.2 are lower than those reported at the optimum pH (4.5); however the residual activity at pH 3.2 is sufficient to be of interest for further immobilization and applications in winemaking. All kinetic parameters of both biocatalysts (LYZ-CA and LYZ-TSA) are altered after immobilization, probably due to the structural modifications in the active site caused by covalent attachment to the supports. The half-life calculated at 25 °C was 39 h for free LYZ, while it increased to 280 and 134 h for LYZ-TSA and LYZ-CA, respectively. This result indicates that immobilization improves the enzyme stability and that LYZ can be utilized in wine applications in its immobilized forms. In addition, LYZ-TSA seems to be the best biocatalyst for further applications in winemaking.
Keywords: Hen egg-white lysozyme; Micro-size magnetic particles; Oenococcus oeni ; Enzyme immobilization; Kinetic parameters; Stability

A haloalkaliphilic bacterium was isolated from salt-enriched soil of Mithapur, Gujarat (India) and identified as Bacillus agaradhaerens Mi-10-62 based on 16S rRNA sequence analysis (NCBI gene bank accession, GQ121032). The bacterium was studied for its α-amylase characteristic in the presence of organic solvents. The enzyme was quite active and it retained considerable activity in 30% (v/v) organic solvents, dodecane, decane, heptane, n-hexane, methanol, and propanol. At lower concentrations of solvents, the catalysis was quite comparable to control. Enzyme catalysis at wide range of alkanes and alcohol was an interesting finding of the study. Mi-10-62 amylase retained activity over a broader alkaline pH range, with the optimal pH at 10–11. Two molars of salt was optimum for catalysis in the presence of most of the tested solvents, though the enzyme retained significant activity even at 4 M salt. With dodecane, the optimum temperature shifted from 50 °C to 60 °C, while the enzyme was active up to 80 °C. Over all, the present study focused on the effect of organic solvents on an extracellular α-amylase from haloalkaliphilic bacteria under varying conditions of pH, temperature, and salt.
Keywords: Haloalkaliphilic bacteria; Organic solvent tolerance; Amylase

Decomposition of Insoluble and Hard-to-Degrade Animal Proteins by Enzyme E77 and Its Potential Applications by Hui Zhao; Shinji Mitsuiki; Mikako Takasugi; Masashi Sakai; Masatoshi Goto; Hiroaki Kanouchi; Tatsuzo Oka (1758-1768).
Insoluble and hard-to-degrade animal proteins are group of troublesome proteins, such as collagen, elastin, keratin, and prion proteins that are largely generated by the meat industry and ultimately converted to industrial wastes. We analyzed the ability of the abnormal prion protein-degrading enzyme E77 to degrade insoluble and hard-to-degrade animal proteins including keratin, collagen, and elastin. The results indicate that E77 has a much higher keratinolytic activity than proteinase K and subtilisin. Maximal E77 keratinolytic activity was observed at pH 12.0 and 65 °C. E77 was also adsorbed by keratin in a pH-independent manner. E77 showed lower collagenolytic and elastinolytic specificities than proteinase K and subtilisin. Moreover, E77 treatment did not damage collagens in ovine small intestines but did almost completely remove the muscles. We consider that E77 has the potential ability for application in the processing of animal feedstuffs and sausages.
Keywords: Insoluble and hard-to-degrade animal proteins; E77; Keratinase; Collagenase; Potential application

An extracellular lipase-producing fungus was isolated from oil-rich soil. This fungus belongs to the genus Rhizopus and clades with Rhizopus oryzae. Lipase was purified to homogeneity from this novel fungal source using ammonium sulphate precipitation followed by Q-Sepharose chromatography. The extracellular lipase was purified 8.6–fold, and enzymatic properties were studied. The molecular mass of the purified enzyme was estimated to be 17 kD by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and 16.25 kD by matrix-assisted laser desorption ionization/time-of-flight analysis. The native molecular mass was estimated to be 17.5 kD by gel filtration, indicating the protein to be monomer. The optimum pH and temperature for the enzyme catalysis were 7.0 °C and 40 °C, respectively. Enzyme was stable in pH range 6.0–7.0 and retains 95–100% activity when incubated at 50 °C for 1 h. The pI of the purified lipase was 4.2. Enzyme was stable in the organic solvents such as ethanol, hexane and methanol for 2 h. Purified enzyme was used for transesterification of oleic acid in the presence of ethanol for production of oleic acid ethyl ester with a conversion efficiency of 66% after 24 h at 30 °C.
Keywords: Lipase; Purification; Rhizopus ; Low molecular weight; Transesterification

A mutant Cs3512, which showed better fermentation of xylose and the mixtures of xylose and glucose, was obtained through mutation of Candida shehatae ATCC 22984 and screening with a medium containing antimycin A and TTC (2,3,5-triphenyltetrazolium chloride). Cs3512 produced 44.4 g/l of ethanol from 121.3 g/l of xylose, which was 13% higher than that by ATCC 22984. At the same time, xylitol production was reduced by 38% to 10.2 g/l from 16.3 g/l by ATCC 22984. Cs3512 also showed 8% increase in ethanol yield from 0.39 to 0.42 g/g comparing to ATCC 22984 when fermenting the sugar mixture composed of 52.9 g/l glucose and 21.2 g/l xylose. When Cs3512 was used in the simultaneous saccharification and fermentation of lime pretreated rice straw via CaCCO (calcium capturing by carbonation) process, it produced ethanol at 77% of the theoretical yield. The results imply that Cs3512 is a potential non-recombinant yeast strain for ethanol production from lignocellulosic biomass.
Keywords: Candida shehatae ; Mutation; Xylose; SSF; Rice straw

Production and Accumulation of 4-O-Methyl-α-d-Glucuronosyl-Xylotriose by Growing Culture of Thermophilic Anoxybacillus sp. Strain JT-12 by Jitladda Thitikorn-amorn; Khin Lay Kyu; Kazuo Sakka; Khanok Ratanakhanokchai (1791-1800).
A thermophilic Anoxybacillus sp. strain JT-12, isolated from soil, produced acidic xylotriose, 4-O-methyl-α-d-glucuronosyl-xylotriose (MeGlcAX3), as a main product from birchwood xylan and accumulated them in the culture under optimum conditions at pH 7.0 and 55 °C using 0.75% (w/v) birchwood xylan as a carbon source for 42–72 h. The acidic xylotriose was purified by ethanol precipitation and high-performance liquid chromatography using NH2 Lichosher® 100 column. The results of electrospray ionization mass spectrometry, mass to charge ratio (m/z) 603.23, confirmed that the purified sample was acidic xylotriose that had benefits and applications in many fields.
Keywords: Acidic xylotriose; Anoxybacillus sp.; 4-O-methyl-α-d-glucuronosyl-xylotriose; Thermophilic bacterium; Xylanolytic enzymes

Synthesis of Pure meso-2,3-Butanediol from Crude Glycerol Using an Engineered Metabolic Pathway in Escherichia coli by Soojin Lee; Borim Kim; Kyungmoon Park; Youngsoon Um; Jinwon Lee (1801-1813).
meso-2,3-Butanediol (meso-2,3-BDO) is essential for the synthesis of various economically valuable biosynthetic products; however, the production of meso-2,3-BDO from expensive carbon sources is an obstacle for industrial applications. In this study, genes involved in the synthesis of 2,3-BDO in Klebsiella pneumoniae were identified and used to genetically modify Escherichia coli for meso-2,3-BDO production. Two 2,3-BDO biosynthesis genes—budA, encoding acetolactate, and meso-budC, encoding meso-SADH—from K. pneumoniae were cloned into the pUC18 plasmid and introduced into E. coli. In 2 l batch culture, the SGSB03 E. coli strain yielded meso-2,3-BDO at 0.31 g/gglucose (with a maximum of 15.7 g/lculture after 48 h) and 0.21 g/gcrude glycerol (with a maximum of 6.9 g/lculture after 48 h). Batch cultures were grown under optimized conditions (aerobic, 6% carbon source, 37 °C, and initial pH 7). To find the optimal culture conditions for meso-2,3-BDO production, we evaluated the enzyme activity of meso-SADH and the whole cell conversion yield (meso-2,3-BDO/acetoin) of the E. coli SGSB02, which contains pSB02. meso-SADH showed high enzyme activity at 30–37 °C and pH 7 (30.5–41.5 U/mg of protein), and the conversion yield of SGSB02 E. coli was highest at 37–42 °C and a pH of 7 (0.25–0.28 g meso-2,3-BDO/gacetoin).
Keywords: meso-2,3-Butanediol; Crude glycerol; Klebsiella pneumonia ; Escherichia coli ; Gene manipulation; Metabolic pathway engineering

The present study characterized the glycoproteins synthesized by buffalo oviduct. Scanning electron microscopy analyses of the ampullary and isthmic segments of cyclic and acyclic buffaloes showed ultrastructural variations in ciliated and nonciliated cells. Mucosal proteins were extracted by scrapping of different segments of oviduct and, after centrifugation, the remainder tissues were subjected to establish primary cell culture system of oviduct epithelial cells and conditioned media were prepared. Time- and concentration-dependent effects of trypsinization on the establishment of primary monolayer culture showed that 0.25% trypsin for 1–2 min at 37 °C were the optimal conditions. Total protein content in oviductal tissues and conditioned media was quantified and analyzed by SDS-PAGE which showed marked variation in different segments of the oviduct. Western blot analysis revealed five major oviduct-specific glycoproteins (OGPs) in cyclic oviduct (ampulla and isthmus) with Mw 180, 95, 75, 66 and 35 kDa in the oviduct extract and two glycoproteins with Mw 95 and 66 kDa in conditioned media. However, in acyclic oviduct (ampulla and isthmus), three glycoproteins were immunostained with Mw 180, 95 and 66 kDa in the oviduct extract and one glycoprotein with Mw 66 kDa in conditioned media. Indirect Enzyme-Linked Immuno Sorbent Assay (ELISA) results showed significant differences of OGPs in different segments of cyclic and acyclic buffaloes and, thus, indicative of segmental variation in the synthesis and secretion of glycoproteins. Oviductal extract secretes more amounts of OGPs as compared to the conditioned medium. The role of these OGPs may be defined and exploited for influencing the fertilization process and/or subsequent embryonic development.
Keywords: Oviduct; Cell culture; Trypsinization; Viability; Oviduct-specific glycoproteins (OGPs); Microenvironment

Low molecular weight endo-xylanase from Bacillus pumilus SSP-34 was purified to homogeneity using ion exchange and size exclusion chromatographies. Xylanases were isolated by novel purification protocol which includes the use of anion exchange matrix such as DEAE Sepharose CL 6B with less affinity towards enzyme protein. The purified B. pumilus SSP-34 have a molecular weight of 20 kDa, with optimum pH and temperature at 6.0 and 50 °C, respectively. The enzyme was stable at 50 °C for 30 min. It showed remarkable stability at pH values ranging from 4.5 to 9 when the reaction was carried out at 50 °C. K m and V max values, determined with oats spelts xylan were 6.5 mg ml−1 and 1,233 μmol min−1 mg−1 protein, respectively, and the specific activity was 1,723 U mg−1
Keywords: Xylanase; SSP 34; Bacillus pumilus ; Cation; Anion; Size exclusion; Chromatography; Purification; Thermostable enzyme

A Potential Commercial Source of Fucoxanthin Extracted from the Microalga Phaeodactylum tricornutum by Sang Min Kim; Yu-Jin Jung; Oh-Nam Kwon; Kwang Hyun Cha; Byung-Hun Um; Donghwa Chung; Cheol-Ho Pan (1843-1855).
Fucoxanthin, one of the main marine carotenoids, is abundant in macro- and microalgae. Here, fucoxanthin was isolated and structurally identified as the major carotenoid in the diatom Phaeodactylum tricornutum through chromatographic and spectroscopic methods, such as liquid chromatography–positive-ion atmospheric pressure chemical ionization/mass spectroscopy and nuclear magnetic resonance. This pigment was quantified by reverse-phase high-performance liquid chromatography, and a number of extraction procedures were assessed to investigate the effect of solvent type, extraction time, temperature, and extraction method (maceration, ultrasound-assisted extraction, Soxhlet extraction, and pressurized liquid extraction). Among the investigated solvents, ethanol provided the best fucoxanthin extraction yield (15.71 mg/g freeze-dried sample weight). Fucoxanthin content in the extracts produced by the different methods was quite constant (15.42–16.51 mg/g freeze-dried sample weight) but increased steeply based on the percentage of ethanol in water, emphasizing the importance of ethanol in the extraction. The results indicate that P. tricornutum is a rich source of fucoxanthin (at least ten times more abundant than that in macroalgae) that is easily extracted with ethanol, suggesting potential applications in human and animal food, health, and cosmetics.
Keywords: Microalgae; Phaeodactylum tricornutum ; Carotenoid; Fucoxanthin; Extraction; Diatom

Pretreatment of Rice Straw Using a Butanone or an Acetaldehyde Dilute Solution Explosion for Producing Ethanol by Jian Zhang; Wen-Xue Zhang; Jian Yang; Yue-Hong Liu; Xia Zhong; Zheng-Yun Wu; Kenji Kida; Yu Deng (1856-1870).
Ethanol conversion from rice straw using butanone and acetaldehyde dilute solution explosions was evaluated based on the optimization of pure water explosion. To decrease residual inhibitor content, the exploded slurry was dried and investigated at different temperature. Using a 0.9-mol/L butanone solution explosion, with the explosion pressure set at 3.1 MPa, the residence time at 7 min, the dried rice straw-to-water ratio at 1:3 (w/w), and the exploded slurry drying temperuture at 90 °C for 8 h, the yields of total sugar, glucose, and xylose were 85%, 88%, 82% (w/w), respectively, and the ethanol productivity was 26.0 g/100 g rice straw dry matter. Moreover, 0.5-mol/L acetaldehyde dilute solution explosion improved the efficiency of enzymatic hydrolysis (EH) and simultaneous saccharification and co-fermentation (SSCF), and the residual inhibitors had negligible effects on EH and SSCF after detoxification by drying. The results suggested that compared with pure water explosions, the use of butanone and of acetaldehyde dilute solution explosions lowered the explosive temperature and improved the sugar yield, although relative crystallinity of the rice straw dry matter was increased after the explosion.
Keywords: Rice straw; Bioethanol; Butanone; Acetaldehyde; Solution explosion; Drying detoxification