Enzymatic Inhibition By Lignin During Second Generation Ethanol Production

An important hindrance to commercialization of lignocellulosic ethanol is the high cost of enzymes. Reducing enzyme loadings is necessary to reduce costs. Knowledge of the inhibitors of these enzymes is necessary to better inform enzyme development and process design. Five factors have been identified: soluble inhibitors, solid lignin adsorption, product inhibition, mixing efficiency and oxygen deactivation of the enzymes that hydrolyze cellulose to glucose. These factors are intertwined and properly assessing them individually require the elimination of the others. Isolating each factor, however, has not been done throughout literature leading to lumped constants. Soluble inhibitors reduce conversion sharply leading to high enzyme loadings and impeding the evaluation of any of the other factors. Through washing, the soluble inhibitors may be eliminated, and only washed biomass (either sugar cane bagasse or corn stover) was used to study the other factors. This work further investigates adsorption on lignin, mixing, and the effect of air on washed pretreated sugarcane bagasse and corn stover. Studies of enzyme adsorption on lignin, showed lignin/enzyme interaction was temperature dependent and proportional to pretreatment severity. Lowering reaction temperatures to 30°C, eliminated enzyme adsorption and was opposite to what was expected, indicating a possible entropic process. On a practical basis, the additional free enzyme partial makes up for the lower activity of the enzyme mixture that occurs due to reduced reaction rate at the lower temperature of 30°C. Lower hydrolysis rates also require longer reaction times to achieve the same extent of conversion to glucose. An alternative to counter adsorption of enzyme on lignin occurs by regulating the amount of lignin exposed by adjusting pretreatment conditions. At higher temperatures a large portion of lignin is solubilized and redeposited, increasing lignin exposure and adsorption is higher. At a lower severity, lignin is less exposed, and adsorption is lower. However, higher severity is needed to increase the accessibility of cellulose, thereby facilitating accessibility and conversion. For sugarcane bagasse a 10.74 severity pretreatment (200°C for 20 minute) using liquid hot water resulted in minimal protein adsorption and therefore was interpreted to coincide with a small extent of lignin exposure, as qualitatively confirmed using SEM. Efficient conversion (71- 76%) was achieved when hydrolysis with 6.5 mg of Cellic CTEC3 / g total solids. A more recalcitrant biomass would require a more intense pretreatment to be hydrolyzed at satisfactory levels. Mixing and product inhibition were more intricately linked than the others. When efficient mixing was achieved, product inhibition was decreased relative to cases where mixing was not readily achieved. In these runs, concentrations of pretreated and washed corn stover were at initial concentrations of 10 to 200 g/L. At 200 g/L, the higher efficiency led to faster liquefaction of biomass in the early stages. Faster liquefaction resulted in significantly high glucose conversions (up to 47% final yields) after 72 hours of hydrolysis compared to minimally liquefied material where conversion was 34% Efficient mixing allowed deactivation due to air to be evaluated properly. This factor is the least understood in the literature and has a potentially major effect on the amount enzyme required for a given level of hydrolysis. Deactivation was isolated and observed by measuring conversion in a mixed 1 L reactor either in the presence of absence of air, except in these experiments with a different enzyme formulation, Cellic CTEC2 was used at 3.6 mg protein (Cellic CTEC2) / g solids. Cellic CTEC2 has lower activity, and the lower amount ensured that differences between the two conditions would be more obvious. Air was shown to decrease conversion by 10 to 15% with lower loss of activity corresponding to high solids loading. The impact of unfavorable conditions (presence of lignin, inefficient mixing and inadequate air exposure) can be minimized by adjusting the biomass pretreatment and hydrolysis processes. The extent of adsorption of cellulolytic enzymes on lignin can be reduced by lowering hydrolysis temperature or reducing pretreatment severity. Efficient mixing facilitates liquefaction and increases final glucose conversion from cellulose compared to inefficient mixing methods. Limiting the presence of air increases enzyme activity and the associated final conversions. Adoption of the combined adjustments reduced enzyme loading by 50% (from 6 FPU to 3 FPU / g solids) for the enzyme Cellic CTEC2

Sugarcane bagasse hydrolysis enhancement using BSA

Lignocellulose is composed of polysaccharides linked to lignin and other aromatic compounds, making the sugars not readily available to fermentation. This entails that biomass must go through the unit operations of pretreatment and enzyme hydrolysis. Pretreatment opens the structure to allow the enzymes to act on and hydrolyze cellulose and hemicellulose to glucose and/or xylose which in turn are fermented to ethanol. Concomitantly, the enzymes interact with soluble phenols and insoluble solids derived from lignin that inhibit hydrolysis. This leads to high enzyme loadings and higher production costs. Soluble phenols can be eliminated through washing. Insoluble lignin, however, demands another approach. Using bovine serum albumin (BSA) and pretreated sugarcane bagasse, the effect of blocking solid lignin from adsorbing enzymes during hydrolysis after 72 hours was evaluated. Hydrolysis was carried using 6.25 FPU (Cellulase 13P) and 12.5 IU (Novozyme 188) /g solids (10 mg protein/g solids) at pH 4.8 and 50°C. The conversion was generally higher when BSA was present, 51% (±1%) vs 42% (±1%) with 1.5% solids loading and 46% (±1%) vs 40% (±1%) with 8% solids loading. The use of BSA produced an increase in the final conversion (p-value \u3c 0.001), but conversion decreased as loadings increased. This has been observed in multiple other studies and cannot be explained by a single factor. The basis of this phenomenon is being investigated. Initial experiments that adjusted the enzyme preparation to 2.5 FPU/g glucan (10.5 mg protein/g glucan) of Cellic CTEC3 and improved the mixing of the slurry elevated the conversion to 72% (±5%) without BSA and 76% (±10%) with it, at 1% (w/v) solids loading and 73% (±6%) without BSA and 80% (±10%) with it, at 10% (w/v) solids loading

"The Keynesian Roots of Stock-flow Consistent Macroeconomic Models: Peering Over the Edge of the Short Period"

This paper argues that institutionally rich stock-flow consistent models—that is, models in which economic agents are identified with the main social categories/institutional sectors of actual capitalist economies, the short period behavior of these agents is thoroughly described, and the "period by period" balance sheet dynamics implied by the latter is consistently modeled—are (1) perfectly compatible with John Maynard Keynes's theoretical views, (2) the ideal tool for rigorous post-Keynesian analyses of the medium run, and (3) therefore crucial to the consolidation of the broad post-Keynesian research program.

"Revisiting (and Connecting) Marglin-Bhaduri and Minsky--An SFC Look at Financialization and Profit-led Growth"

Many heterodox strands of thought share both a concern with the study of different phases or growth regimes in the history of capitalism and the use of formal short-run models as an analytical tool. This text suggests that (1) this strategy is potentially misleading; (2) that the stock-flow consistent (SFC) approach, while providing a general framework that may facilitate the dialogue among those currents, is particularly well suited to all those who think that macroeconomic models may illuminate historical quests; and (3) that the main intuitions may be conveyed through the "benchmark" Post Keynesian SFC model presented by Dos Santos and Zezza (2008), dispensing with the complex computer simulations that are normally employed by SFC authors.

LIMITAÇÕES LOGÍSTICAS PARA EXPORTAÇÃO: O CASO DOS PRODUTOS LÁCTEOS BRASILEIROS

O propósito desta pesquisa é avaliar a estrutura do agribusiness do leite no Brasil, identificando as principais limitações logísticas para exportação. Especificamente pretende identificar as principais empresas exportadoras de produtos lácteos, os produtos mais exportados e os países de destino; relatar as maneiras mais freqüentes de inserção dos produtos no mercado externo; e mencionar as estruturas físicas utilizadas pelas empresas para realizarem suas exportações, avaliando suas vantagens e limitações. A presente pesquisa é qualitativa e de natureza exploratória. Como resultado constatou-se que o leite em pó é o produto mais exportado (em volume) seguido do leite condensado; entre os continentes principais importadores de lácteos brasileiros, a África se destacou com o maior número de países, seguida dos países da América do Sul; a forma mais freqüente de inserção dos derivados lácteos no mercado externo é por meio de tradings; dentre os principais problemas logísticos para se exportar mencionados, pode-se citar os rodoviários, portuários, burocráticos; greves e fiscalização, altos custos de pedágios, atrasos e quarentena, falta de contêineres disponíveis e insegurança do processo. Diante tais resultados pode-se dizer que as estruturas logísticas impõem limites ao comércio internacional de lácteos no Brasil. ------------------------------------------------------- The purpose of this research is to evaluate the structure of the agribusiness of milk in Brazil, identifying the main logistic limitations for export. Specifically it intends to identify the main export companies of milk products, the most exported products and the destination countries; to tell the most frequent ways of product insertion in the world market; and to mention the physical structures used by the companies to accomplish their exports, evaluating their advantages and limitations. The present research is qualitative and of exploratory nature. As a result it was verified that the powdered milk is the most exported product (in volume) followed by the condensed milk. Among the main importer continents of Brazilian milk products, Africa stood out with the largest number of countries, followed by the countries of South America. The most frequent form of insertion of dairy products in the external market is through trading. Among the main logistic problems to export, it can be mentioned the roads, ports, bureaucratic processes; inspections and strikes, high costs of tolls and fees, delays and quarantines, lack of available containers and insecurity of the process. With such results it can be said that the logistic structures impose limits to the international trade of milk in Brazil.Comércio Internacional, Logística, Derivados Lácteos, International trade, Logistics, Dairy products, International Relations/Trade, Livestock Production/Industries,

CLASSE TRABALHADORA E O POPULISMO

Livro: LEAL, Murilo. A reinvenção da classe trabalhadora (1953-1964). Campinas/SP: Editora da Unicamp, 2011, 517 p

Berkeley e Mandeville: religião e moralidade

The purpose of this text is to analyze the debate between Berkeley’s Alciphron and Mandeville’s The fable of the bees and Letter to Dion, focusing on the questions indirectly raised by Berkeley to his opponent: Would there be a place for religion in Mandeville’s society or in his social, political and economic system? If so, what role would it play? Without religion, on what foundations would morality in social life be based?Key words: Berkeley, Mandeville, morality.O objetivo deste texto é analisar o debate entre Berkeley, na obra Alciphron, e Mandeville, na “A fábula das abelhas” e “Carta para Dion”, tendo como centro da discussão as questões indiretamente levantadas por Berkeley para seu oponente: Na sociedade pensada por Mandeville ou em seu sistema social, político e econômico, haveria um lugar para a religião? E, se há algum lugar, qual seu papel? Sem a religião, o que fundamentaria a moralidade na vida social?Palavras-chave: Berkeley, Mandeville, moralidade