RESUMO
Plant biomass is the most abundant renewable resource in nature. In a circular economy perspective, the implementation of its bioconversion into fermentable sugars is of great relevance. Lytic Polysaccharide MonoOxygenases (LPMOs) are accessory enzymes able to break recalcitrant polysaccharides, boosting biomass conversion and subsequently reducing costs. Among them, auxiliary activity of family 9 (AA9) acts on cellulose in synergism with traditional cellulolytic enzymes. Here, we report for the first time, the production of the AA9 LPMOs from the mesophilic Trichoderma reesei (TrAA9B) and the thermophilic Thermoascus aurantiacus (TaAA9B) microorganisms in tobacco by plastid transformation with the aim to test this technology as cheap and sustainable manufacture platform. In order to optimize recombinant protein accumulation, two different N-terminal regulatory sequences were used: 5' untranslated region (5'-UTR) from T7g10 gene (DC41 and DC51 plants), and 5' translation control region (5'-TCR), containing the 5'-UTR and the first 14 amino acids (Downstream Box, DB) of the plastid atpB gene (DC40 and DC50 plants). Protein yields ranged between 0.5 and 5% of total soluble proteins (TSP). The phenotype was unaltered in all transplastomic plants, except for the DC50 line accumulating AA9 LPMO at the highest level, that showed retarded growth and a mild pale green phenotype. Oxidase activity was spectrophotometrically assayed and resulted higher for the recombinant proteins without the N-terminal fusion (DC41 and DC51), with a 3.9- and 3.4-fold increase compared to the fused proteins.
Assuntos
Proteínas Fúngicas , Oxigenases de Função Mista , Celulose/química , Proteínas Fúngicas/biossíntese , Oxigenases de Função Mista/biossíntese , Polissacarídeos/metabolismo , Nicotiana/metabolismo , Plantas Geneticamente Modificadas/metabolismo , PlastídeosRESUMO
In a circular economy era the transition towards renewable and sustainable materials is very urgent. The development of bio-based solutions, that can ensure technological circularity in many priority areas (e.g., agriculture, biotechnology, ecology, green industry, etc.), is very strategic. The agricultural and fishing industry wastes represent important feedstocks that require the development of sustainable and environmentally-friendly industrial processes to produce and recover biofuels, chemicals and bioactive molecules. In this context, the replacement, in industrial processes, of chemicals with enzyme-based catalysts assures great benefits to humans and the environment. In this review, we describe the potentiality of the plastid transformation technology as a sustainable and cheap platform for the production of recombinant industrial enzymes, summarize the current knowledge on the technology, and display examples of cellulolytic enzymes already produced. Further, we illustrate several types of bacterial auxiliary and chitinases/chitin deacetylases enzymes with high biotechnological value that could be manufactured by plastid transformation.
Assuntos
Biocombustíveis , Biotecnologia , Humanos , Plastídeos/química , Resíduos Industriais/análise , AgriculturaRESUMO
The aim of this paper is to make the point on the fortieth years study on the ß-glycosidase from Sulfolobus solfataricus. This enzyme represents one of the thermophilic biocatalysts, which is more extensively studied as witnessed by the numerous literature reports available since 1980. Comprehensive biochemical studies highlighted its broad substrate specificity for ß-d-galacto-, gluco-, and fuco-sides and also showed its remarkable exo-glucosidase and transglycosidase activities. The enzyme demonstrated to be active and stable over a wide range of temperature and pHs, withstanding to several drastic conditions comprising solvents and detergents. Over the years, a great deal of studies were focused on its homotetrameric tridimensional structure, elucidating several structural features involved in the enzyme stability, such as ion pairs and post-translational modifications. Several ß-glycosidase mutants were produced in the years in order to understand its peculiar behavior in extreme conditions and/or to improve its functional properties. The ß-glycosidase overproduction was also afforded reporting numerous studies dealing with its production in the mesophilic host Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, and Lactococcus lactis. Relevant applications in food, beverages, bioenergy, pharmaceuticals, and nutraceutical fields of this enzyme, both in free and immobilized forms, highlighted its biotechnological relevance.
Assuntos
Proteínas Arqueais/química , Biotecnologia/história , Glucosidases/química , Sulfolobus solfataricus/enzimologia , Proteínas Arqueais/história , Estabilidade Enzimática , Glucosidases/história , História do Século XX , História do Século XXI , Especificidade por SubstratoRESUMO
Non-Saccharomyces yeasts are metabolically active during grape must fermentations and can contribute with enzymes and metabolites to enhance the complexity and to define the final wine aroma. Nowadays, the use of non-Saccharomyces yeasts in combination with Saccharomyces cerevisiae is a state-of-the art strategy to improve wine composition and/or wine sensory properties. The present paper deals with the new yeast strains of Metschnikowia fructicola and S. cerevisiae, that were selected as representatives of the yeast microbiota isolated from grapes and grape juice of Aglianico cultivar. S. cerevisiae was utilized both as single strain starter and in combination with M. fructicola in experimental fermentations of Aglianico must. The dynamic of yeast populations was evaluated during the fermentation process analyzing the wine volatile compounds profile. The volatile compounds were identified by SPME-GC/MS. The results, showed that the multiple indigenous yeast starter was able to modulate the volatile compounds profiles and improve the aromatic complexity of wine, with a higher content of esters and terpenes.
RESUMO
In this work, a new exploitation of the thermostable ß-glycosidase from Sulfolobus solfataricus expressed in Saccharomyces cerevisiae to create functional foods for low lactose diets was evaluated. For this purpose, the lactose hydrolysis reaction using immobilized and soluble enzymes was investigated. Activity and stability at different conditions of pH and temperature were tested. The immobilization process had a big impact on the catalysis performance, leading to an enhancement of the enzymatic reaction rate on lactose, as demonstrated by the increasing of 2 and 2.5 folds of Kcat and Kcat /KM , respectively. Moreover, the maximal activity for the immobilized form was referred at pH 6.5 instead of 7.0, leading to an improvement of the catalytic performance at milk pHs. Although the soluble enzyme was already weakly inhibited by the reaction products, the immobilization further reduced the inhibitory action of glucose increasing the Ki from 96.7 to 110.4 mM. Finally, the immobilized enzyme showed high hydrolysis rate in whole milk that yielded 99% of lactose breakdown in 10 and 30 min at 60 and 40°C, respectively. These results support the application of the immobilized ß-glycosidase for the development of new functional foods particularly suitable to the alleviation of lactose intolerance.
Assuntos
Glicosídeo Hidrolases/metabolismo , Lactose/metabolismo , Leite/química , Temperatura , Animais , Bovinos , Quitosana/química , Estabilidade Enzimática , Enzimas Imobilizadas/metabolismo , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Sulfolobus/enzimologiaRESUMO
We have isolated a novel exopolysaccharide (EPS) produced by the extreme halophilic archaeon Haloterrigena turkmenica. Some features, remarkable from an industrial point of view, such as emulsifying and antioxidant properties, were investigated. H. turkmenica excreted 20.68 mg of EPS per 100 ml of culture medium when grown in usual medium supplemented with glucose. The microorganism excreted the biopolymer mainly in the middle exponential growth phase and reached the maximal production in the stationary phase. Analyses by anion exchange chromatography and SEC-TDA Viscotek indicated that the EPS was composed of two main fractions of 801.7 and 206.0 kDa. It was a sulfated heteropolysaccharide containing glucose, galactose, glucosamine, galactosamine, and glucuronic acid. Studies performed utilizing the mixture of EPS anionic fractions showed that the biopolymer had emulsifying activity towards vegetable oils comparable or superior to that exhibited by the controls, moderate antioxidant power when tested with 2,2'-diphenyl-1-picrylhydrazyl (DPPH(·)), and moisture-retention ability higher than hyaluronic acid (HA). The EPS from H. turkmenica is the first exopolysaccharide produced by an archaea to be characterized in terms of properties that can have potential biotechnological applications.
Assuntos
Halobacteriales/metabolismo , Polissacarídeos/biossíntese , Polissacarídeos/química , Antioxidantes/química , Antioxidantes/metabolismo , Biotecnologia , Compostos de Bifenilo/farmacologia , Meios de Cultura/química , Emulsões , Galactose/metabolismo , Glucose/metabolismo , Halobacteriales/química , Ácido Hialurônico/metabolismo , Picratos/farmacologiaRESUMO
BACKGROUND: Cellulases and xylanases are the key enzymes involved in the conversion of lignocelluloses into fermentable sugars. Western Ghat region (India) has been recognized as an active hot spot for the isolation of new microorganisms. The aim of this work was to isolate new microorganisms producing cellulases and xylanases to be applied in brewer's spent grain saccharification. RESULTS: 93 microorganisms were isolated from Western Ghat and screened for the production of cellulase and xylanase activities. Fourteen cellulolytic and seven xylanolytic microorganisms were further screened in liquid culture. Particular attention was focused on the new isolate Bacillus amyloliquefaciens XR44A, producing xylanase activity up to 10.5 U mL-1. A novel endo-1,4-beta xylanase was identified combining zymography and proteomics and recognized as the main enzyme responsible for B. amyloliquefaciens XR44A xylanase activity. The new xylanase activity was partially characterized and its application in saccharification of brewer's spent grain, pretreated by aqueous ammonia soaking, was investigated. CONCLUSION: The culture supernatant of B. amyloliquefaciens XR44A with xylanase activity allowed a recovery of around 43% xylose during brewer's spent grain saccharification, similar to the value obtained with a commercial xylanase from Trichoderma viride, and a maximum arabinose yield of 92%, around 2-fold higher than that achieved with the commercial xylanase. © 2014 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
RESUMO
An extracellular thermo-alkali-stable and cellulase-free xylanase from Geobacillus thermodenitrificans A333 was purified to homogeneity by ion exchange and size exclusion chromatography. Its molecular mass was 44 kDa as estimated in native and denaturing conditions by gel filtration and SDS-PAGE analysis, respectively. The xylanase (GtXyn) exhibited maximum activity at 70 °C and pH 7.5. It was stable over broad ranges of temperature and pH retaining 88 % of activity at 60 °C and up to 97 % in the pH range 7.5-10.0 after 24 h. Moreover, the enzyme was active up to 3.0 M sodium chloride concentration, exhibiting at that value 70 % residual activity after 1 h. The presence of other metal ions did not affect the activity with the sole exceptions of K(+) that showed a stimulating effect, and Fe(2+), Co(2+) and Hg(2+), which inhibited the enzyme. The xylanase was activated by non-ionic surfactants and was stable in organic solvents remaining fully active over 24 h of incubation in 40 % ethanol at 25 °C. Furthermore, the enzyme was resistant to most of the neutral and alkaline proteases tested. The enzyme was active only on xylan, showing no marked preference towards xylans from different origins. The hydrolysis of beechwood xylan and agriculture-based biomass materials yielded xylooligosaccharides with a polymerization degree ranging from 2 to 6 units and xylobiose and xylotriose as main products. These properties indicate G. thermodenitrificans A333 xylanase as a promising candidate for several biotechnological applications, such as xylooligosaccharides preparation.
Assuntos
Proteínas de Bactérias/química , Geobacillus/enzimologia , Glucuronatos/metabolismo , Oligossacarídeos/metabolismo , Xilosidases/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/metabolismo , Clonagem Molecular , Estabilidade Enzimática , Geobacillus/química , Geobacillus/genética , Concentração de Íons de Hidrogênio , Peso Molecular , Especificidade por Substrato , Temperatura , Xilosidases/genética , Xilosidases/isolamento & purificação , Xilosidases/metabolismoRESUMO
The fungal arabinofuranosidase from Pleurotus ostreatus PoAbf recombinantly expressed in Pichia pastoris rPoAbf and its evolved variant rPoAbf F435Y/Y446F were tested for their effectiveness to enhance the enzymatic saccharification of three lignocellulosic biomasses, namely Arundo donax, corn cobs and brewer's spent grains (BSG), after chemical or chemical-physical pretreatment. All the raw materials were subjected to an alkaline pretreatment by soaking in aqueous ammonia solution whilst the biomass from A. donax was also pretreated by steam explosion. The capability of the wild-type and mutant rPoAbf to increase the fermentable sugars recovery was assessed by using these enzymes in combination with different (hemi)cellulolytic activities. These enzymatic mixtures were either entirely of commercial origin or contained the cellulase from Streptomyces sp. G12 CelStrep recombinantly expressed in Escherichia coli in substitution to the commercial counterparts. The addition of the arabinofuranosidases from P. ostreatus improved the hydrolytic efficiency of the commercial enzymatic cocktails on all the pretreated biomasses. The best results were obtained using the rPoAbf evolved variant and are represented by increases of the xylose recovery up to 56.4%. These data clearly highlight the important role of the accessory hemicellulolytic activities to optimize the xylan bioconversion yields.
Assuntos
Glicosídeo Hidrolases/metabolismo , Lignina/metabolismo , Pleurotus/enzimologia , Biomassa , Clonagem Molecular , Escherichia coli/enzimologia , Escherichia coli/genética , Expressão Gênica , Glicosídeo Hidrolases/genética , Hidrólise , Pichia/enzimologia , Pichia/genética , Pleurotus/genética , Pleurotus/metabolismo , Streptomyces/enzimologia , Streptomyces/genéticaRESUMO
An intracellular ß-xylosidase (AbXyl), from the thermoalkaline Anoxybacillus sp. 3M, was purified and characterized. The homodimeric enzyme (140â¯kDa) was optimally active at 65⯰C and pHâ¯5.5, exhibited half life of 10â¯h at 60⯰C, 78 and 88% residual activity after 24â¯h, at pHâ¯4.5 and 8.0, respectively. Fe2+, Cu2+, Al3+, Ag+ and Hg2+ inhibited the enzyme; the activity was moderately stimulated by SDS and not influenced by ß-mercaptoethanol. In the presence of p-nitrophenyl-ß-d-xylopyranoside, AbXyl exhibited Km of 0.19â¯mM, Kcat of 453.29â¯s-1, Kcatâ¯Km-1 of 2322â¯s-1â¯mM and was moderately influenced by xylose (Ki 21.25â¯mM). The enzyme hydrolyzed xylo-oligomers into xylose and catalyzed transxylosilation reactions also in presence of alcohols as acceptors, producing xylo-oligosaccharides and alkyl-xylosides. Finally AbXyl was applied towards a statistically optimized process of brewery's spent grain bioconversion, highlighting the important role of this biocatalyst in reaching high yields of fermentable sugars.
Assuntos
Agricultura , Anoxybacillus/enzimologia , Carboidratos/química , Resíduos Industriais , Xilosidases/metabolismo , Anoxybacillus/citologia , Inibidores Enzimáticos/farmacologia , Concentração de Íons de Hidrogênio , Hidrólise , Espaço Intracelular/enzimologia , Especificidade por Substrato , Temperatura , Xilosidases/antagonistas & inibidoresRESUMO
BACKGROUND: Biofuels production from plant biomasses is a complex multi-step process with important economic burdens. Several biotechnological approaches have been pursued to reduce biofuels production costs. The aim of the present study was to explore the production in tobacco plastome of three genes encoding (hemi)cellulolytic enzymes from thermophilic and hyperthermophilic bacterium and Archaea, respectively, and test their application in the bioconversion of an important industrially pretreated biomass feedstock (A. donax) for production of second-generation biofuels. RESULTS: The selected enzymes, endoglucanase, endo-ß-1,4-xylanase and ß-glucosidase, were expressed in tobacco plastome with a protein yield range from 2 % to more than 75 % of total soluble proteins (TSP). The accumulation of endoglucanase (up to 2 % TSP) gave altered plant phenotypes whose severity was directly linked to the enzyme yield. The most severe seedling-lethal phenotype was due to the impairment of plastid development associated to the binding of endoglucanase protein to thylakoids. Endo-ß-1,4-xylanase and ß-glucosidase, produced at very high level without detrimental effects on plant development, were enriched (fourfold) by heat treatment (105.4 and 255.4 U/mg, respectively). Both plastid-derived biocatalysts retained the main features of the native or recombinantly expressed enzymes with interesting differences. Plastid-derived xylanase and ß-glucosidase resulted more thermophilic than the E. coli recombinant and native counterpart, respectively. Bioconversion experiments, carried out at 50 and 60 °C, demonstrated that plastid-derived enzymes were able to hydrolyse an industrially pretreated giant reed biomass. In particular, the replacement of commercial enzyme with plastid-derived xylanase, at 60 °C, produced an increase of both xylose recovery and hydrolysis rate; whereas the replacement of both xylanase and ß-glucosidase produced glucose levels similar to those observed with the commercial cocktails, and xylose yields always higher in the whole 24-72 h range. CONCLUSIONS: The very high production level of thermophilic and hyperthermophilic enzymes, their stability and bioconversion efficiencies described in this study demonstrate that plastid transformation represents a real cost-effective production platform for cellulolytic enzymes.
RESUMO
Twenty-four Actinobacteria strains, isolated from Arundo donax, Eucalyptus camaldulensis and Populus nigra biomass during natural biodegradation and with potential enzymatic activities specific for the degradation of lignocellulosic materials, were identified by a polyphasic approach. All strains belonged to the genus Streptomyces (S.) and in particular, the most highly represented species was Streptomyces argenteolus representing 50% of strains, while 8 strains were identified as Streptomyces flavogriseus (synonym S. flavovirens) and Streptomyces fimicarius (synonyms Streptomyces acrimycini, Streptomyces baarnensis, Streptomyces caviscabies, and Streptomyces flavofuscus), and the other four strains belonged to the species Streptomyces drozdowiczii, Streptomyces rubrogriseus, Streptomyces albolongus, and Streptomyces ambofaciens. Moreover, all Streptomyces strains, tested for endo and exo-cellulase, cellobiase, xylanase, pectinase, ligninase, peroxidase, and laccase activities using qualitative and semi-quantitative methods on solid growth medium, exhibited multiple enzymatic activities (from three to six). The 24 strains were further screened for endo-cellulase activity in liquid growth medium and the four best endo-cellulase producers (S. argenteolus AE58P, S. argenteolus AE710A, S. argenteolus AE82P, and S. argenteolus AP51A) were subjected to partial characterization and their enzymatic crude extracts adopted to perform saccharification experiments on A. donax pretreated biomass. The degree of cellulose and xylan hydrolysis was evaluated by determining the kinetics of glucose and xylose release during 72 h incubation at 50°C from the pretreated biomass in the presence of cellulose degrading enzymes (cellulase and ß-glucosidase) and xylan related activities (xylanase and ß-xylosidase). The experiments were carried out utilizing the endo-cellulase activities from the selected S. argenteolus strains supplemented with commercial ß-gucosidase and xylanase preparations from Genencore (Accellerase BG and Accellerase XY). Cellulose and xylan conversion, when conducted using commercial (hemi)cellulases, gave glucose and xylose yields of 30.17 and 68.9%, respectively. The replacement of the cellulolytic preparation from Genencor (Accellerase 1500), with the endo-cellulase from S. argenteolus AE58P resulted in almost 76% of the glucose yield obtained in the presence of the commercial counterpart. Due to the promising results obtained by using the enzymatic crude extracts from S. argenteolus AE58P in the pretreated A. donax saccharification experiments, the proteins putatively responsible for endo-cellulase activity in this strain were identified by proteomics. Several proteins were confidently identified in different Streptomyces spp., eight of which belong to the class of Carbohydrate active enzymes. Overall results highlighted the biotechnological potential of S. argenteolus AE58P being an interesting candidate biocatalyst-producing bacterium for lignocellulose conversion and production of biochemicals and bioenergy.
RESUMO
An enzymatic mixture of cellulases and xylanases was produced by Pleurotus ostreatus using microcrystalline cellulose as inducer, partially characterized and tested in the statistical analysis of Arundo donax bioconversion. The Plackett-Burman screening design was applied to identify the most significant parameters for the enzymatic hydrolysis of pretreated A. donax. As the most significant influence during the enzymatic hydrolysis of A. donax was exercised by the temperature (°C), pH, and time, the combined effect of these factors in the bioconversion by P. ostreatus cellulase and xylanase was analyzed by a 3(3) factorial experimental design. It is worth noting that the best result of 480.10 mg of sugars/gds, obtained at 45 °C, pH 3.5, and 96 hours of incubation, was significant also when compared with the results previously reached by process optimization with commercial enzymes.
Assuntos
Carboidratos/síntese química , Celulases/química , Celulose/química , Endo-1,4-beta-Xilanases/química , Pleurotus/enzimologia , Poaceae/química , Carboidratos/isolamento & purificação , Técnicas de Química Combinatória/métodos , Extratos Vegetais/químicaRESUMO
Evaluation of phenolic profile, antioxidant power, and protective capacity against oxidation of red blood cells (RBCs) of olive oil phenolic extracts (OOPEs) from several Italian varieties were studied. Phenolic profiles, and quantification of seven selected bioactive compounds were performed by RP-HPLC. OOPEs exhibited high antioxidant activity, and this capacity was positively related to their phenolic amount. In particular, OOPE5 (cv Gentile di Larino, Molise region) displayed the highest phenolic and ortho-diphenolic content as well as the strongest scavenging activity determined using 2,2'-diphenyl-1-picrylhydrazyl (DPPH) (87% DPPH inhibition). Protective capacity against stressed RBCs was investigated through the evaluation of methemoglobin (MetHb) and malondialdehyde (MDA) levels. OOPE5 was the most active against methemoglobin production (53.7% reduction), whereas OOPE1 (cv Lavagnina, Liguria region) showed the highest protection toward malondialdehyde (83.3% reduction). Overall the selected oils showed qualitative and quantitative differences in phenol composition, and this variability influenced their protective effect against oxidative damages.
Assuntos
Azeite de Oliva/química , Fenóis/análise , Óleos de Plantas/química , Antioxidantes/química , Humanos , Itália , Estresse OxidativoRESUMO
Six Lactobacillus strains were analyzed to select a bacterium for conversion of brewers' spent grain (BSG) into lactic acid. Among the investigated strains, L. acidophilus ATCC 43121 showed the highest yield of lactic acid production (16.1 g/L after 48 hours) when grown in a synthetic medium. It was then analyzed for its ability to grow on the hydrolysates obtained from BSG after acid-alkaline (AAT) or aqueous ammonia soaking (AAS) pretreatment. The lactic acid production by L. acidophilus ATCC 43121 through fermentation of the hydrolysate from AAS treated BSG was 96% higher than that from the AAT treated one, although similar yields of lactic acid per consumed glucose were achieved due to a higher (46%) glucose consumption by L. acidophilus ATCC 43121 in the AAS BSG hydrolysate. It is worth noting that adding yeast extract to the BSG hydrolysates increased both the yield of lactic acid per substrate consumed and the volumetric productivity. The best results were obtained by fermentation of AAS BSG hydrolysate supplemented by yeast extract, in which the strain produced 22.16 g/L of lactic acid (yield of 0.61 g/g), 27% higher than the value (17.49 g/L) obtained in the absence of a nitrogen source.
Assuntos
Grão Comestível/metabolismo , Fermentação , Ácido Láctico/biossíntese , Lactobacillus acidophilus/metabolismo , Amônia/química , Meios de Cultura , Grão Comestível/química , Glucose/química , Ácido Láctico/química , Lactobacillus acidophilus/química , Nitrogênio/químicaRESUMO
The messenger RNA (mRNA) differential display technique was applied to the identification and isolation of genes whose transcription was altered in leaves of Prunus armeniaca infected by European stone fruit yellows (ESFY) phytoplasma belonging to ribosomal subgroup 16SrX-B. Four genes whose steady-state levels of expression significantly changed in response to phytoplasma infection were isolated and identified. The results obtained show that two group of genes are affected by phytoplasma infection in apricot leaves. The first group comprises genes that are up-regulated by phytoplasma presence: in particular, a gene encoding the heat-shock protein HSP-70, a gene encoding a metallothionein (MT) and another homologous to the EST 673 cDNA clone of P. armeniaca, whose function was unknown. The other gene identified in our analysis is down-regulated by phytoplasma presence. It encodes a protein having homology to an amino acid transporter of Arabidopsis thaliana. Our findings demonstrate the usefulness of mRNA differential display approach for the detection of plant metabolic pathways affected by phytoplasma infection.
Assuntos
Perfilação da Expressão Gênica , Phytoplasma/crescimento & desenvolvimento , Folhas de Planta/genética , Prunus/genética , RNA Mensageiro/genética , Northern Blotting , DNA Complementar/química , DNA Complementar/genética , DNA Complementar/isolamento & purificação , Regulação da Expressão Gênica de Plantas , Folhas de Planta/microbiologia , Prunus/microbiologia , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Análise de Sequência de DNARESUMO
Chestnut shell (CS) is an agronomic residue mainly used for extraction of antioxidants or as adsorbent of metal ions. It also contains some polysaccharide that has not been considered as potential source of fermentable sugars for biofuel production until now. In this study, the effect of different pretreatment methods on CS was evaluated in order to obtain the greatest conversion of cellulose and xylan into fermentable sugars. Hot acid impregnation, steam explosion (acid-catalysed or not), and aqueous ammonia soaking (AAS) were selected as pretreatments. The pretreated biomass was subjected to saccharification with two enzyme cocktails prepared from commercial preparations, and evaluation of the best pretreatment and enzyme cocktail was based on the yield of fermentable sugars produced. As AAS provided the best result after preliminary experiments, enhancement of sugar production was attempted by changing the concentrations of ammonium hydroxide, enzymes, and CS. The optimal pretreatment condition was 10 % ammonium hydroxide, 70 °C, 22 h with CS at 5 % solid loading. After saccharification of the pretreated CS for 72 h at 50 °C and pH 5.0 with a cocktail containing cellulase (Accellerase 1500), beta-glucosidase (Accellerase BG), and xylanase (Accellerase XY), glucose and xylose yields were 67.8 and 92.7 %, respectively.
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Aesculus/química , Amônia/química , Carboidratos/síntese química , Celulase/química , Endo-1,4-beta-Xilanases/química , Nozes/química , beta-Glucosidase/química , Agricultura/métodos , Fermentação , Resíduos Industriais/prevenção & controle , VaporRESUMO
The increasing production of several plastics such as expanded polystyrene, widely used as packaging and building materials, has caused the release of considerable amounts of pentane employed as an expanding agent. Today many microorganisms are used to degrade hydrocarbons in order to minimize contamination caused by several industrial activities. The aim of our work was to identify a suitable microorganism to degrade pentane. We focused our attention on a strain of Arthrobacter sp. which in a shake-flask culture produced 95% degradation of a 10% mixture of pentane in a minimal medium after 42 days of incubation at 20 degrees C. Arthrobacter sp. cells were immobilized on a macroporous polystyrene particle matrix that provides a promising novel support for cell immobilization. The method involved culturing cells with the expanded polystyrene in shake-flasks, followed by in situ growth within the column. Scanning electron microscopy analysis showed extensive growth of Arthrobacter sp. on the polymeric surface. The immobilized microorganism was able to actively degrade a 10% mixture of pentane, allowing us to obtain a bioconversion yield of 90% after 36 h. Moreover, in repeated-batch operations, immobilized Arthrobacter sp. cells were able to maintain 85-95% pentane degradation during a 2 month period. Our results suggest that this type of bioreactor could be used in pentane environmental decontamination.