Pentose Sugars Research Articles

"Bial’s Test, A Simple Method for Formaldehyde Detection"

Current high-fidelity formaldehyde detection in waterbased samples requires chemical derivatization followed by ion chromatography or liquid chromatography [1-3]. These methods are labor intensive and require expensive instrumentation. Here, we propose an additional method for detecting and quantifying aqueous formaldehyde that is based on Bial’s test and simple photometric equipment. Our approach also allows for a convenient qualitative color test that is applicable to samples with high formaldehyde concentrations. The foundation of our method was developed by Bial in the form of a colorimetric test for identifying pentose sugars in the urine of patients with pentosuria [4]. Bial’s solution consist of orcinol, hydrochloric acid, and iron (III) chloride [4]. The concentrations of the components vary from study to study and some authors have substituted hydrochloric acid with ethanol [5] When heated with pentose sugars, Bial’s solution reacts to form furfurals and changes color from a light pale yellow to blue or green [6].

Fast Scan Cyclic Voltammetry As a DNA Sensor Using Carbon Fiber Microelectrodes

Over the past five decades and since the discovery of the structure of nucleic acids (DNA and RNA), different technological advancements have been achieved to understand the overall biochemical properties of nucleic acids. The electrochemical reactivity of these nucleobases defines the overall reactivity of DNA. So far, technological progress on the development of electrochemical DNA biosensors has been applied on different biomedical and environmental analyses which includes, analysis of infectious diseases, diagnosis and treatment of cancer and extensive studies on neurodegenerative and genetic diseases. As nucleic acids are the profound and vital biomolecules of all living things, they are still the center of intensive research. The building blocks of DNA are purine bases, adenine and guanine and pyrimidine bases, thymine and cytosine, where each base is attached to the pentose sugar with phosphate group.Fast scan cyclic voltammetry (FSCV) is an electroanalytical technique which applies a voltage in a fast (greater than 400 V/s) and repeating manner to a working electrode and records the resultant current produced by oxidation of analyte at the electrode surface. Previous research by Venton and colleagues has shown that the electroactive nucleosides and nucleotides can be oxidized at a voltage of a specific waveform, using carbon fiber-microelectrode (CFME). The applied voltage can only oxidize specific nucleobases such as purines and the peak oxidative current is analyzed to quantify the concentration of the analyte.When co-detecting the purine nucleosides, the two primary oxidative peaks interfere with each other. As a result, a scalene waveform for the co-detection of adenosine and guanosine, initially developed by Ross et. al, was adapted to help with the co-detection of purine bases adenine and guanine in DNA. The used waveform sweeps up at 150 V/s from -0.4 to 1.45 V and sweeps back at 400V/s vs. a silver-silver chloride (Ag/AgCl) reference electrode. Adenine was recorded to have two oxidative peaks at 1.34 V on the backward scan (primary peak) and another at 1 V on the forward scan (secondary scan). The two peaks come from the oxidation of C2 and C8 into ketones. In addition, guanine was recorded to have two oxidative peaks at 1.2 V on the forward scan (primary peak) and another at 0.7 V on the backward scan (secondary peak). The two peaks are from the oxidation of C8 into a ketone and the oxidation of N7 after it has lost its hydrogen from the oxidation of C8. The structure of the DNA sample, (ssDNA, dsDNA, synthetic DNA, bacterial DNA, short base pairs and longer base pairs), determines the shape and measurement of the peak oxidative current of adenine and guanine, which is a molecular fingerprint for analyte detection. Due to the nature of DNA, we are able to amplify and manipulate it using biochemical methods. However, nucleic acid base pairing has to be taken into account and a strategy to detect target sequences with an electrode must be implemented. Based on the analyzed data from this experiment, this analytical method and measurement can be useful in detecting different physical and structural DNA damage and opens a way for studies on a potentially new diagnostic and treatment mechanisms. This work could potentially develop an entire new class of biosensors for DNA, RNA, and other nucleic acids, which would have lasting impacts in the field of sensor diagnostics.

Nonmetabolizable Arabinose Inhibits Vibrio cholerae Growth in M9 Medium with Gluconate as the Sole Carbon Source.

The serogroups O1 and O139 of the marine bacterium Vibrio cholerae are responsible for causing cholera in humans. The pentose sugar arabinose is nonmetabolizable by the pathogen and is present in environmental niches as well as in the human intestine. In this study, arabinose-mediated V. cholerae growth interference was assessed in M9 minimal medium containing gluconate as the sole carbon source in the light of Entner-Doudoroff (ED) pathway, an obligatory metabolic route for gluconate utilization. V. cholerae O1 and O139 strains failed to grow in the presence of ≥ 0.3% arabinose in M9 with 0.2% gluconate, but there was no growth inhibition in the presence of arabinose in M9 with 0.2% glucose. Transcriptional analysis of edd and eda, the genes constituting the ED pathway, showed ~100- and ~17-fold increases, respectively, in M9-gluconate. Minor increases of ~4- and ~2-fold for edd and eda, respectively, were noted in AKI medium supplemented with 0.5% arabinose. The observed arabinose-mediated growth inhibition can contribute toward deepening the understanding of altered phenotypes, if any, via complementation/expression studies in V. cholerae with pBAD vectors and arabinose as an inducer.

Heterologous expression of genes for bioconversion of xylose to xylonic acid in Corynebacterium glutamicum and optimization of the bioprocess

In bacterial system, direct conversion of xylose to xylonic acid is mediated through NAD-dependent xylose dehydrogenase (xylB) and xylonolactonase (xylC) genes. Heterologous expression of these genes from Caulobacter crescentus into recombinant Corynebacterium glutamicum ATCC 13032 and C. glutamicum ATCC 31831 (with an innate pentose transporter, araE) resulted in an efficient bioconversion process to produce xylonic acid from xylose. Process parameters including the design of production medium was optimized using a statistical tool, Response Surface Methodology (RSM). Maximum xylonic acid of 56.32 g/L from 60 g/L xylose, i.e. about 76.67% of the maximum theoretical yield was obtained after 120 h fermentation from pure xylose with recombinant C. glutamicum ATCC 31831 containing the plasmid pVWEx1 xylB. Under the same condition, the production with recombinant C. glutamicum ATCC 13032 (with pVWEx1 xylB) was 50.66 g/L, i.e. 69% of the theoretical yield. There was no significant improvement in production with the simultaneous expression of xylB and xylC genes together indicating xylose dehydrogenase activity as one of the rate limiting factor in the bioconversion. Finally, proof of concept experiment in utilizing biomass derived pentose sugar, xylose, for xylonic acid production was also carried out and obtained 42.94 g/L xylonic acid from 60 g/L xylose. These results promise a significant value addition for the future bio refinery programs.

Exploiting new biorefinery models using non-conventional yeasts and their implications for sustainability

Feasible bioprocessing of lignocellulosic biomass requires the use of microbial strains with tolerance to inhibitor compounds and osmotic pressure, able to provide high product yield and productivity. In this sense, this study evaluated the potential of two non-conventional yeasts, Hansenula polymorpha CBS 4732 and Debaryomyces hansenii CBS 767, for use on biomass conversion in a biorefinery perspective. The ability of the strains to consume pentose and hexose sugars, to resist the toxic compounds present in hydrolysates, as well as to produce sugar alcohols and ethanol, was investigated. H. polymorpha showed highlighted resistance to toxic compounds and relevant ability to consume xylose and produce xylitol and ethanol under these conditions, at 37 °C. D. hansenii was a great producer of arabitol from glucose. The implications for sustainability due to the use of these yeasts in biorefineries was discussed. These results open up new perspectives for the development of the biorefinery sector.

Taxogenomic assessment and genomic characterisation of Weissella cibaria strain 92 able to metabolise oligosaccharides derived from dietary fibres

The importance of the gut microbiota in human health has led to an increased interest to study probiotic bacteria. Fermented food is a source of already established probiotics, but it also offers an opportunity to discover new taxa. Four strains of Weissella sp. isolated from Indian fermented food have been genome sequenced and classified into the species W. cibaria based on whole-genome phylogeny. The genome of W. cibaria strain 92, known to utilise xylooligosaccharides and produce lactate and acetate, was analysed to identify genes for oligosaccharide utilisation. Clusters including genes involved in transportation, hydrolysis and metabolism of xylooligosaccharides, arabinooligosaccharides and β-glucosides were identified. Growth on arabinobiose and laminaribiose was detected. A 6-phospho-β-glucosidase clustered with a phosphotransferase system was found upregulated during growth on laminaribiose, indicating a mechanism for laminaribiose utilisation. The genome of W. cibaria strain 92 harbours genes for utilising the phosphoketolase pathway for the production of both acetate and lactate from pentose and hexose sugars but lacks two genes necessary for utilising the pentose phosphate pathway. The ability of W. cibaria strain 92 to utilise several types of oligosaccharides derived from dietary fibres, and produce lactate and acetate makes it interesting as a probiotic candidate for further evaluation.

High carbohydrate diets increase respiratory quotients above 1 due to lipid synthesis

The respiratory quotient (RQ, carbon dioxide emission/oxygen consumption) is believed to range from 0.7–1 depending on the fuels used for catabolism. However, RQ can rise above 1 when CO2 is released without oxygen consumption. This can occur when hexose sugars are catabolized to pentose sugars via the pentose phosphate pathway to produce NADPH for glutathione regeneration. It is also hypothesized RQs > 1 can occur under lipid synthesis when glucose is catabolized by glycolysis to acetylCOA. However, to our knowledge, no prior studies have assessed animal RQ during periods of carbohydrate conversion to lipid. We used stop‐flow respirometry to measure RQ values for nymphal South American locusts (Schistocerca cancellata) that had been consuming artificial diets varying in carbohydrate:protein ratio for 3–5 days. For locusts measured during the hour after a meal, RQ values increased as the carbohydrate:protein content of the previously‐consumed diet increased, to a maximal value of 1.2. Locusts consuming diets high in carbohydrate:protein ratio synthesized fat at high rates, consistent with the hypothesis that an RQ above 1 is an indicator of synthesis of lipid from carbohydrate.Support or Funding InformationThis research was supported by NSF IOS‐1826848 and BARD FI‐575‐18.

The Xylose Metabolizing Yeast Spathaspora passalidarum is a Promising Genetic Treasure for Improving Bioethanol Production

Currently, the fermentation technology for recycling agriculture waste for generation of alternative renewable biofuels is getting more and more attention because of the environmental merits of biofuels for decreasing the rapid rise of greenhouse gas effects compared to petrochemical, keeping in mind the increase of petrol cost and the exhaustion of limited petroleum resources. One of widely used biofuels is bioethanol, and the use of yeasts for commercial fermentation of cellulosic and hemicellulosic agricultural biomasses is one of the growing biotechnological trends for bioethanol production. Effective fermentation and assimilation of xylose, the major pentose sugar element of plant cell walls and the second most abundant carbohydrate, is a bottleneck step towards a robust biofuel production from agricultural waste materials. Hence, several attempts were implemented to engineer the conventional Saccharomyces cerevisiae yeast to transport and ferment xylose because naturally it does not use xylose, using genetic materials of Pichia stipitis, the pioneer native xylose fermenting yeast. Recently, the nonconventional yeast Spathaspora passalidarum appeared as a founder member of a new small group of yeasts that, like Pichia stipitis, can utilize and ferment xylose. Therefore, the understanding of the molecular mechanisms regulating the xylose assimilation in such pentose fermenting yeasts will enable us to eliminate the obstacles in the biofuels pipeline, and to develop industrial strains by means of genetic engineering to increase the availability of renewable biofuel products from agricultural biomass. In this review, we will highlight the recent advances in the field of native xylose metabolizing yeasts, with special emphasis on S. passalidarum for improving bioethanol production.

Bioconversión sostenible de residuos agrícolas sacarificados en bioetanol por Wickerhamomyces anomalus

Snowballing levels of greenhouse gas emissions and concerns about climate change has led to an ongoing exploration of biofuels. Bioethanol can be obtained from wheat straw and can be readily available as clean fuel for combustion engines. Therefore, Wickerhamomyces anomalus yeast strain IHZ-26 was used to produce bioethanol from sugar solution obtained from enzymatic hydrolysis of wheat straw. Nineteen different fermentation media were used for this purpose in which carbon source employed was sugar solution obtained from enzymatic hydrolysis of wheat straw. Out of which, maximum bioethanol yield (1.09 g/L; p <0.05) was observed in ‘C1 Yeast extract, peptone, glucose’ medium. After optimization of different cultural parameters, surface culture fermentation for 5 days at 25℃ gave maximum results using 2, 1.5 and 2 g of glucose, xylose and ammonium dihydrogen phosphate, respectively. Four hours old inoculum of yeast in a concentration of 3.5% was optimized for maximum bioethanol yield. These optimized parameters resulted in augmented bioethanol production (5.0g/L) by 5.02 folds. This study revelas that W. anomalus IHZ-26 employed was able to covert pentose and hexose sugars simultaneously with efficient ethanol yield.

Quantitative trait loci (QTL) underlying phenotypic variation in bioethanol-related processes in Neurospora crassa.

Bioethanol production from lignocellulosic biomass has received increasing attention over the past decade. Many attempts have been made to reduce the cost of bioethanol production by combining the separate steps of the process into a single-step process known as consolidated bioprocessing. This requires identification of organisms that can efficiently decompose lignocellulose to simple sugars and ferment the pentose and hexose sugars liberated to ethanol. There have been many attempts in engineering laboratory strains by adding new genes or modifying genes to expand the capacity of an industrial microorganism. There has been less attention in improving bioethanol-related processes utilizing natural variation existing in the natural ecotypes. In this study, we sought to identify genomic loci contributing to variation in saccharification of cellulose and fermentation of glucose in the fermenting cellulolytic fungus Neurospora crassa through quantitative trait loci (QTL) analysis. We identified one major QTL contributing to fermentation of glucose and multiple putative QTL’s underlying saccharification. Understanding the natural variation of the major QTL gene would provide new insights in developing industrial microbes for bioethanol production.

Substrate utilization of ethanologenic yeasts co-cultivation of Pichia kudriavzevii and Saccharomyces cerevisiae

Bioethanol is one of the renewable alternative energies and can be used as a substitute for fossil fuels. Bioethanol is produced from a fermentation process, which is assisted by microbial yeast groups (ethanologenic yeast). Yeast Pichia kudriavzevii is capable of converting both carbon source pentose and hexose sugars to ethanol. In the previous study, P. kudriavzevii ethanol stress - tolerant mutant strains T5 was successfully constructed via directed mutagenesis thus suggesting their potential as fermentation agent. One strategy to increase ethanol production is by applying co-cultivation techniques. Thus, this study aimed to examine the ability of sugar substrate utilization by ethanologenic yeast S. cerevisiae and P. kudriavzeviiat various inoculum ratio. The results of the study indicated that no antagonist interaction detected between S. cerevisiae with all of P. kudriavzevii, both mutant and wild type strains. Based on sugar consumption analysis, both yeast isolates could be used in ethanol production simultaneously to maximize mixed substrate utilization. Our study revealed that the best sugar consumption found on co-cultivation of S. cerevisiae with wild type P. kudriavzevii T (wt) in 1: 1 inoculum ratio.

The pentose phosphate pathway of cellulolytic clostridia relies on 6-phosphofructokinase instead of transaldolase

The genomes of most cellulolytic clostridia do not contain genes annotated as transaldolase. Therefore, for assimilating pentose sugars or for generating C5 precursors (such as ribose) during growth on other (non-C5) substrates, they must possess a pathway that connects pentose metabolism with the rest of metabolism. Here we provide evidence that for this connection cellulolytic clostridia rely on the sedoheptulose 1,7-bisphosphate (SBP) pathway, using pyrophosphate-dependent phosphofructokinase (PPi-PFK) instead of transaldolase. In this reversible pathway, PFK converts sedoheptulose 7-phosphate (S7P) to SBP, after which fructose-bisphosphate aldolase cleaves SBP into dihydroxyacetone phosphate and erythrose 4-phosphate. We show that PPi-PFKs of Clostridium thermosuccinogenes and Clostridium thermocellum indeed can convert S7P to SBP, and have similar affinities for S7P and the canonical substrate fructose 6-phosphate (F6P). By contrast, (ATP-dependent) PfkA of Escherichia coli, which does rely on transaldolase, had a very poor affinity for S7P. This indicates that the PPi-PFK of cellulolytic clostridia has evolved the use of S7P. We further show that C. thermosuccinogenes contains a significant SBP pool, an unusual metabolite that is elevated during growth on xylose, demonstrating its relevance for pentose assimilation. Last, we demonstrate that a second PFK of C. thermosuccinogenes that operates with ATP and GTP exhibits unusual kinetics toward F6P, as it appears to have an extremely high degree of cooperative binding, resulting in a virtual on/off switch for substrate concentrations near its K½ value. In summary, our results confirm the existence of an SBP pathway for pentose assimilation in cellulolytic clostridia.

Efficiency of Xylitol Production from Meyerozyma caribbica Y67 with Cell Initiation and Volume Fermentation

One of the rare types of pentose sugar is xylitol, which has various benefits in the field of food and medicine. Xylitol is one of the results of xylose fermentation and few microorganisms are able to produce it. Meyerozyma caribbica Y67 is one of the yeast collections of Indonesian Culture Collection (InaCC) which can produce xylitol. The production of xylitol about cell initiation and media volume gave different results for each factor. The fermentation conditions were using erlenmeyer 250 mL, agitation 150 rpm and 30ºC temperature. The parameters analyzed were dry cell weight (DCW), xylose, and xylitol. The results of this study showed that cell initiation with an optical density at 600 nm (OD600) = 5 (≍1.07x107 CFU or 3.980 g/L) had the highest efficiency in producing xylitol for 24 hours of fermentation, 51, 099%; specific growth rate (µ): 0.069. In the media volume variable, for 24 hours fermentation, the high-efficiency value of 20% volume erlenmeyer is 55, 708%; (µ): 0.082 and 48 hours fermentation is 40% volume erlenmeyer which is 71, 959%; (µ): 0.048. The research is expected to be used as a scale up recommendation for the industry.

Engineering of Pentose Transport in Saccharomyces cerevisiae for Biotechnological Applications.

Lignocellulosic biomass yields after hydrolysis, besides the hexose D-glucose, D-xylose, and L-arabinose as main pentose sugars. In second generation bioethanol production utilizing the yeast Saccharomyces cerevisiae, it is critical that all three sugars are co-consumed to obtain an economically feasible and robust process. Since S. cerevisiae is unable to metabolize pentose sugars, metabolic pathway engineering has been employed to introduce the respective pathways for D-xylose and L-arabinose metabolism. However, S. cerevisiae lacks specific pentose transporters, and these sugars enter the cell with low affinity via glucose transporters of the Hxt family. Therefore, in the presence of D-glucose, utilization of D-xylose and L-arabinose is poor as the Hxt transporters prefer D-glucose. To solve this problem, heterologous expression of pentose transporters has been attempted but often with limited success due to poor expression and stability, and/or low turnover. A more successful approach is the engineering of the endogenous Hxt transporter family and evolutionary selection for D-glucose insensitive growth on pentose sugars. This has led to the identification of a critical and conserved asparagine residue in Hxt transporters that, when mutated, reduces the D-glucose affinity while leaving the D-xylose affinity mostly unaltered. Likewise, mutant Gal2 transporter have been selected supporting specific uptake of L-arabinose. In fermentation experiments, the transporter mutants support efficient uptake and consumption of pentose sugars, and even co-consumption of D-xylose and D-glucose when used at industrial concentrations. Further improvements are obtained by interfering with the post-translational inactivation of Hxt transporters at high or low D-glucose concentrations. Transporter engineering solved major limitations in pentose transport in yeast, now allowing for co-consumption of sugars that is limited only by the rates of primary metabolism. This paves the way for a more economical second-generation biofuels production process.

Engineering of Saccharomyces cerevisiae for efficient fermentation of cellulose.

Conversion of lignocellulosic biomass to biofuels using microbial fermentation is an attractive option to substitute petroleum-based production economically and sustainably. The substantial efforts to design yeast strains for biomass hydrolysis have led to industrially applicable biological routes. Saccharomyces cerevisiae is a robust microbial platform widely used in biofuel production, based on its amenability to systems and synthetic biology tools. The critical challenges for the efficient microbial conversion of lignocellulosic biomass by engineered S. cerevisiae include heterologous expression of cellulolytic enzymes, co-fermentation of hexose and pentose sugars, and robustness against various stresses. Scientists developed many engineering strategies for cellulolytic S. cerevisiae strains, bringing the application of consolidated bioprocess at an industrial scale. Recent advances in the development and implementation of engineered yeast strains capable of assimilating lignocellulose will be reviewed.

Evaluation of pre-treatment methods for Lantana camara stem for enhanced enzymatic saccharification.

This study evaluates certain pre-treatment methods for Lantana camara stem for efficient conversion to fermentable sugars. The composition analysis of L. camara stem showed 66.8% (w/w) holocellulose, 34.9% (w/w) cellulose and 17% (w/w) hemicellulose. Comparative analysis of various chemical, physical or physico-chemical pre-treatments on L. camara stem was performed. Of all pretreatment methods used, pre-treatment with 1% (v/v) H2SO4 assisted autoclaving gave maximum total reducing sugar yield 132.7mg/g (13.2g/L) of raw biomass in pretreated hydrolysate. Major contribution to total reducing sugar was from hemicellulosic fraction, because total pentose sugar yield was 119.4mg/g of raw biomass whereas, glucose released was only 10mg/g of untreated biomass. The enzymatic saccharification of pre-treated L. camara stem by 1% (v/v) H2SO4 assisted autoclaving was performed with partially purified carboxymethylcellulase from Bacillus amyloliquefaciens SS35. Enzymatic saccharification at 30°C for 48h gave total reducing sugar yield, 63.3mg/g of pre-treated biomass in the hydrolysate, while untreated biomass gave 43.3mg/g of untreated biomass. The total sugar yield i.e. the sum of pre-treated biomass hydrolysate total reducing sugar (132.7mg/g of raw biomass) and enzymatic hydrolysate total reducing sugar (63.3mg/g of pre-treated biomass) was 196.0mg/g of raw biomass, indicating the effectiveness of pre-treatment method. Field emission scanning electron microscopy, Fourier transform infrared and X-ray diffraction analyses displayed enhanced porosity, removal of non-cellulosic sugars and increased cellulose crystallinity, respectively, in pre-treated L. camara stem, showing the effectiveness of acid assisted autoclaving pre-treatment.

Untargeted Metabonomics of Genetically Modified Cows Expressing Lactoferrin Based on Serum and Milk.

Metabolites of serum and milk from genetically modified (GM) cows and contrast check (CK) cows were comparatively investigated. Serum and milk were collected from genetically modified (GM) cows and contrast check (CK) cows, and then, they were analyzed using ultraperformance liquid chromatography-mass spectrometry (UPLC-MS) and gas chromatography-mass spectrometry (GC-MS). Although the level of some blood biochemical indexes for GM cows was shifted up or down, they were generally in normal physiological condition. Serum samples from lactoferrin GM cows exhibited reduced levels of amino acids and elevated levels of indoleacetate, α-keto acids, long-chain fatty acids, etc. GM milk possessed elevated levels of pentose and amino sugar metabolites, including arabitol, xylulose, glucuronate, and N-acetylgalactosamine. Interestingly, some essential nutrients, such as certain unsaturated fatty acids (e.g., eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA)), and some necessary rare sugars were significantly upregulated. Compared to the CK group, a Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis was conducted based on the increased or decreased metabolites identified in the serum and milk samples of the GM group. The results showed that the GM cows were in healthy condition and their milk has improved benefits for customers. The milk from genetically modified cows was found to be a promising milk source for producing recombinant human lactoferrin (rhLF) for human beings.

Designing a cocktail containing redox enzymes to improve hemicellulosic hydrolysate fermentability by microorganisms

Bioproducts production using monomeric sugars derived from lignocellulosic biomass presents several challenges, such as to require a physicochemical pretreatment to improve its conversion yields. Hydrothermal lignocellulose pretreatment has several advantages and results in solid and liquid streams. The former is called hemicellulosic hydrolysate (HH), which contains inhibitory phenolic compounds and sugar degradation products that hinder microbial fermentation products from pentose sugars. Here, we developed and applied a novel enzyme process to detoxify HH. Initially, the design of experiments with different redox activities enzymes was carried out. The enzyme mixture containing the peroxidase (from Armoracia rusticana) together with superoxide dismutase (from Coptotermes gestroi) are the most effective to detoxify HH derived from sugarcane bagasse. Butanol fermentation by the bacteria Clostridium saccharoperbutylacetonicum and ethanol production by the yeast Scheffersomyces stipitis increased by 24.0× and 2.4×, respectively, relative to the untreated hemicellulosic hydrolysates. Detoxified HH was analyzed by chromatographic and spectrometric methods elucidating the mechanisms of phenolic compound modifications by enzymatic treatment. The enzyme mixture degraded and reduced the hydroxyphenyl- and feruloyl-derived units and polymerized the lignin fragments. This strategy uses biocatalysts under environmentally friendly conditions and could be applied in the fuel, food, and chemical industries.

BIOTECHNOLOGICAL STUDIES ON BIOFUEL PRODUCTION FROM AGRICULTURAL WASTES

Four different fruits peels (Banana, Watermelon, Orange and Mango) were chosen to study the possibility to produce biofuel. The starch, pectin, hemicellulose, celluloses, lignin and proteins fractions were determined in terms of dry weights percentages for these peels. The obtained results showed that mango peels recorded the highest oligosaccharides levels, even lignin content was highest by 17.25%. Also, banana peels showed high oligosaccharides levels, with the lowest level of lignin by 4.82%. Aspergillus niger and Phanerochaete chrysosporium were used to degrade fruit peels , where during their degrading enzyme assays the co-cultivation can improve extracellular enzyme secretion. While, the co-cultivation was resulted an increasing in enzymes activities by 5.8, 8.8 and 81.3 nmol.min-1.ml-1 for β-glucosidase, celulase and xylanase, respectively. The SDS-PAGE protein profiles confirmed that, fungi co-cultivation results in improved the excretion of relevant enzymes proteins, the combined profile were contained proteins not observed in the individual fungus culture. The banana and mango peels were released the greatest saccharified pentose and hexose sugars, the total fermentable sugars from them were 27.77 and 21.13 g.l-1, respectively. The co-fermentation were conducted by selected yeast strain belong to Kluyveromyces marxianus to contribute previously sexual regenerative Saccharomyces cerevisiae for bioethanol production. As expected, the co-fermentation increased the bioethanol yield by more than 18% as average percentage for all saccharified peels. The substantial bioethanol yield were observed by saccharifed banana peels with 10.74 g.l-1, the adding of calcium oxide as drying agent lead finally to 97.5 wt % of pure bioethanol by duplicate the distillation process. The reaction molar ratio of cocked oil to ethyl acetate were established by 0.1, 0.125, 0.2, 0.25, 0.5 and 1.0 mol.mol-1 respectively.

Xylose and Arabinose Fermentation to Produce Ethanol by Isolated Yeasts from Durian (Durio zibethinus L.) Fruit

Xylose and arabinose are pentosesugars that present in hemicellulose, part of lignocellulose biomass.These pentose sugars can be fermented by yeast into ethanol.The aim of this research was to utilize yeast isolated from durian fruit (DuriozibethinusL.) in fermentation of xylose and arabinose to produce bioethanol.Phenotypic test of isolates was conducted by growingthe isolates in various agar media, i.e.YPD (Yeast Peptone Dextrose), YPA (Yeast Peptone Arabinose), and YPX (Yeast Peptone Xylose) containing dextrose, arabinose, xylose, respectively, assole carbon source to see cell growth. The yeast isolates were further identified using API AOC 20C kit method. Yeast isolates were applied for fermentation of glucose, arabinose, and xylosein incubated cultures. Ethanol production in the fermentation was analyzed bygaschromatography. Yeast isolates were identified as Kodamaea ohmeri, Candida famata, Candida guilliermondii, and Crytococcuc laurentii. Based on gas chromatography data, it was found that ethanol produced in the fermentation for three days, the highest ethanol content on xylose substrate was fermented by Candida famata-Awhich is0.021% (v/v) ethanol resulted from initial concentration of 5% xylose (w/v). While on arabinose substrate, the highest ethanol content was fermented by Crytococcus laurentii-Bwhich is 0.0034% (v/v) ethanol resulted from initial concentration of 5% arabinose (w/v).