There is a great interest in increasing the levels of production of nanocellulose, either by adjusting production systems or by improving the raw material. Despite all the advantages and applications, nanocellulose still has a high cost compared to common fibers and to reverse this scenario the development of new, cheaper, and more efficient means of production is required. The market trend is to have an increase in the mass production of nanocellulose; there is a great expectation of world trade. In this sense, research in this sector is on the rise, because once the cost is not an obstacle to production, this material will have more and more market. Production of the cellulose fibers is determinant for the production of nanocellulose by a hydrolyzing agent with a reasonable yield. This work presents several aspects of this new material, mainly addressing the enzymatic pathway, presenting the hydrolysis conditions such as pH, biomass concentration, enzymatic loading, temperature, and time. Also, the commonly used characterization methods are presented, as well as aspects of the nanocellulose production market.

There is tremendous interest in using agro-industrial wastes, such as cellulignin, as starting materials for the production of fuels and chemicals. Cellulignin are the solids, which result from the acid hydrolysis of the sugarcane bagasse. The objective of this work was to optimize the enzymatic hydrolysis of the cellulose fraction of cellulignin, and to study its fermentation to ethanol using Saccharomyces cerevisiae. Cellulose conversion was optimized using response surface methods with pH, enzyme loading, solid percentage, and temperature as factor variables. The optimum conditions that maximized the conversion of cellulose to glucose, calculated from the initial dried weight of pretreated cellulignin, (43 degrees C, 2%, and 24.4 FPU/g of pretreated cellulignin) such as the glucose concentration (47 degrees C, 10%, and 25.6 FPU/g of pretreated cellulignin) were found. The desirability function was used to find conditions that optimize both, conversion to glucose and glucose concentration (47 degrees C, 10%, and 25.9 FPU/g of pretreated cellulignin). The resulting enzymatic hydrolyzate was fermented yielding a final ethanol concentration of 30.0 g/L, in only 10 h, and reaching a volumetric productivity of 3.0 g/L x h, which is close to the values obtained in the conventional ethanol fermentation of sugar cane juice (5.0-8.0 g/L x h) in Brazil.

a b s t r a c tIn this study, we investigated the enzymatic hydrolysis of pretreated sugarcane bagasse using eight different enzymatic blends obtained from concentrated crude enzyme extracts produced by Penicillium funiculosum and Trichoderma harzianum as well as from the extracts in combination with a commercial enzymatic cocktail. The influence of different levels of biomass delignification, degree of crystallinity of lignicellulose, composition of enzymatic activities and BSA on enzymatic hydrolysis yields (HYs) was evaluated. Our X-ray diffraction studies showed that crystallinity of lignocellulose is not a key determinant of its recalcitrance toward enzymatic hydrolysis. In fact, under the experimental conditions of our study, an increase in crystallinity of lignocellulosic samples resulted in increased glucose release by enzymatic hydrolysis. Furthermore, under the same conditions, the addition of BSA had no significant effect on enzymatic hydrolysis. The most efficient enzyme blends were obtained by mixing a commercial enzymatic cocktail with P. funiculosum or T. harzianum cellulase preparations (HYs above 97%) followed by the concentrated extract of P. funiculosum alone (HY = 88.5%). Increased hydrolytic efficiencies appeared to correlate with having an adequate level of both ␤-glucosidase and xylanase activities in the blends.

Aiming to contribute toward the characterization of new, biotechnologically relevant cellulolytic enzymes, we report here the first crystal structure of the catalytic core domain of Cel7A (cellobiohydrolase I) from the filamentous fungus Trichoderma harzianum IOC 3844. Our structural studies and molecular dynamics simulations show that the flexibility of Tyr260, in comparison with Tyr247 from the homologous Trichoderma reesei Cel7A, is enhanced as a result of the short side‐chains of adjacent Val216 and Ala384 residues and creates an additional gap at the side face of the catalytic tunnel. T. harzianum cellobiohydrolase I also has a shortened loop at the entrance of the cellulose‐binding tunnel, which has been described to interact with the substrate in T. reesei Cel7A. These structural features might explain why T. harzianum Cel7A displays higher kcat and Km values, and lower product inhibition on both glucoside and lactoside substrates, compared with T. reesei Cel7A.

Recebido em 13/5/09; aceito em 24/6/09; publicado na web em 25/11/09 PRODUCTION, PROPERTIES AND APPLICATION OF CELLULASES IN THE HYDROLYSIS OF AGROINDUSTRIAL RESIDUES. Cellulases have been intensively studied in the past few years, due to the interests in biofuels production from lignocellulosic materials, since they permit maintaining mild conditions during the conversion process. These enzymes can be produced by a broad variety of naturally occurring microorganisms, such as from genera Aspergillus, Trichoderma, Penicillium and Humicola. Targeting the increasing of expression levels, molecular biology tools have been used for heterologous genes insertion in host cells, e. g., Pichia pastoris and Escherichia coli. Enzymes from fungal cellulolytic complex usually act best at pH between 4 and 5 under temperatures from 40 to 60 °C and can be used for either sequential (SHF) or simultaneous (SSF) hydrolysis together alcoholic fermentation. In this review, the main raw materials for production of cellulases are identified, as well as the state of art of enzymes' properties, production and main applications.Keywords: cellulases; agroindustrial residues; lignocellulose. INTRODUÇÃOCelulases são enzimas que constituem um complexo capaz de atuar sobre materiais celulósicos, promovendo sua hidrólise. Estas enzimas são biocatalisadores altamente específicos que atuam em sinergia para a liberação de açúcares, dos quais glicose é o que desperta maior interesse industrial, devido à possibilidade de sua conversão em etanol. 1,2Estas enzimas começaram a ser estudadas durante a Segunda Guerra Mundial. A deterioração de fardas, barracas, bolsas e demais objetos dos acampamentos, fabricados de algodão, chamou a atenção de soldados das forças armadas norte-americanas, instalados nas ilhas Solomon, no Pacífico Sul. Algumas organizações, como a Quartermaster Corps, juntamente com as forças armadas, montaram laboratórios em busca de explicações e soluções imediatas para esse problema, que incluíam a detecção de organismos agentes das deteriorações, seus mecanismos de ação e métodos de controle. O grupo de trabalho, constituído por oito pesquisadores e liderado pelo Dr. Elwyn T. Reese, passou a conduzir seus experimentos no laboratório das forças armadas, em Natick, Massachusets, Estados Unidos. Como resultado das pesquisas, uma linhagem, codificada como QM6a, de um fungo filamentoso, identificado posteriormente como Trichoderma viride, foi isolada e a esta foi atribuída a característica de excretar enzimas capazes de degradar celulose. Até 1953, Dr. Reese e seu grupo de trabalho já haviam determinado que enzimas naturais, nomeadas celulases, constituem complexos de diversas moléculas com distintas habilidades na degradação do substrato. Em 1956, Dr. Reese aliou seus conhecimentos aos da Dra. Mary Mandels, que, em conjunto, passaram a trabalhar no laboratório em Natick. A partir de então, o foco das pesquisas deixou de ser a prevenção da hidrólise da celulose e passou a ser o melhoramento da produção das enzimas responsáveis por esse fe...

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The objective of this work is to investigate the utilization of two abundant agricultural residues in Brazil for the production and application of cellulolytic enzymes. Different materials obtained after pretreatment of sugarcane bagasse, as well as pure synthetic substrates, were considered for cellulase production by Penicillium funiculosum. The best results for FPase (354 U L(-1)) and beta-glucosidase (1,835 U L(-1)) production were observed when sugarcane bagasse partially delignified cellulignin (PDC) was used. The crude extract obtained from PDC fermentation was then partially characterized. Optimal temperatures for cellulase action ranged from 52 to 58 degrees C and pH values of around 4.9 contributed to maximum enzyme activity. At 37 degrees C, the cellulases were highly stable, losing less than 15% of their initial activity after 23 h of incubation. There was no detection of proteases in the P. funiculosum extract, but other hydrolases, such as endoxylanases, were identified (147 U L(-1)). Finally, when compared to commercial preparations, the cellulolytic complex from P. funiculosum showed more well-balanced amounts of beta-glucosidase, endo- and exoglucanase, resulting in the desired performance in the presence of a lignocellulosic material. Cellulases from this filamentous fungus had a higher glucose production rate (470 mg L(-1) h(-1)) when incubated with corn cob than with Celluclast, GC 220 and Spezyme (312, 454 and 400 mg L(-1) h(-1), respectively).

Succinic acid, a four-carbon diacid, has been the focus of many research projects aimed at developing more economically viable methods of fermenting sugar-containing natural materials. Succinic acid fermentation processes also consume CO(2), thereby potentially contributing to reductions in CO(2) emissions. Succinic acid could also become a commodity used as an intermediate in the chemical synthesis and manufacture of synthetic resins and biodegradable polymers. Much attention has been given recently to the use of microorganisms to produce succinic acid as an alternative to chemical synthesis. We have attempted to maximize succinic acid production by Actinobacillus succinogenes using an experimental design methodology for optimizing the concentrations of the medium components. The first experiment consisted of a 2(4-1) fractional factorial design, and the second entailed a Central Composite Rotational Design so as to achieve optimal conditions. The optimal concentrations of nutrients predicted by the model were: NaHCO(3), 10.0 g l(-1); MgSO(4), 3.0 g l(-1); yeast extract, 2.0 g l(-1); KH(2)PO(4). 5.0 g l(-1); these were experimentally validated. Under the best conversion conditions, as determined by statistical analysis, the production of succinic acid was carried out in an instrumented bioreactor using sugarcane bagasse hemicellulose hydrolysate, yielding a concentration of 22.5 g l(-1).