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

Saberes docentes pedagógicos computacionais e sua elaboração na prática

Este trabalho coloca em pauta os saberes docentes relativos ao uso dos artefatos computacionais no que se refere aos saberes que são elaborados por professores a partir da prática docente. Utilizando os parâmetros da investigação qualitativa, acompanhamos o trabalho desenvolvido por quatro professores de disciplinas de ciências naturais em uma escola pública da cidade de São Paulo, Brasil. Realizamos entrevistas e um acompanhamento do trabalho docente por um período de um ano letivo. Os resultados obtidos revelaram que os professores, ao fazerem uso dos computadores como recurso didático, impulsionados pelo intuito de potenciar a aprendizagem, desenvolveram saberes que denominamos Saberes Docentes Pedagógicos Computacionais Experienciais, principalmente, os relativos ao Uso dos Recursos, da Comunicação, da Busca e do Compartilhamento Digital

A construção participativa de arranjos silvipastoris em São Bonifácio - SC

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias. Programa de Pós-Graduação em AgroecossistemasO presente estudo constitui-se em uma reflexão sobre o processo participativo para construção de arranjos silvipastoris, desenvolvido em São Bonifácio-SC e que teve por objetivo construir coletivamente, entre técnicos e agricultores produtores de leite do município e parceiros externos, arranjos silvipastoris possíveis de serem implantados. O objetivo desta dissertação é identificar e analisar o entendimento coletivo sobre participação entre os atores (técnicos e agricultores) de São Bonifácio-SC, envolvidos na pesquisa participativa sobre arranjos silvipastoris. Para tanto, busca-se evidenciar e discutir algumas das características deste processo na ótica desses atores, bem como apontar as potencialidades e os desafios de se utilizar abordagens participativas em ações de pesquisa-extensão rural. Trata-se de uma pesquisa qualitativa calcada em alguns instrumentos e procedimentos metodológicos, tais como: observação direta e entrevistas semi-estruturadas com atores-chave do processo. Os dados obtidos foram analisados e interpretados seguindo a metodologia de análise de discurso denominada "Discurso do Sujeito Coletivo" (DSC), e evidenciaram que a participação é visualizada de diferentes formas pelos distintos atores-chave. As mesmas características demonstradas pelos atores-chave, ao mesmo tempo que potencializam este e outros processos participativos de pesquisa-extensão rural representam também grandes desafios a serem enfrentados

Caracterização cefalométrica da má oclusão de Classe II, 1ª. divisão, em brasileiros leucodermas

One of the main points in Orthodontic studies is the growth and development of the craniofacial structures. In this study, skeletal cephalometric characteristics of Class II, division 1 malocclusion were assessed in lateral cephalograms. The experimental sample comprised 55 white Brazilian individuals of both genders, with an ANB angle of 4.5 degrees or higher. The mean age of the subjects was 13.5 years. Steiner and McNamara Jr cephalometric analyses were used in order to evaluate the relation between angular and linear positions of the apical bases, the dental and cranial structures, comparing with the values obtained in the control group (available at Bauru Dental School-USP). The results showed that, for the experimental group, the maxilla was well positioned in relation to the cranial base. The maxillomandibular relation showed an increased overjet, which was predictable based on criteria for sample selection. The geometrical proportion of the apical bases presented a small mandible and a normal sized maxilla. The craniofacial growth pattern presented a vertical tendency. The maxillary incisors were buccally inclined and well positioned by the linear evaluation. The mandibular incisors showed marked buccal inclination and protrusion. No statistically significant difference between genders was found.Um dos principais temas em Ortodontia é o estudo do crescimento e desenvolvimento craniofacial. Neste estudo, a caracterização cefalométrica da Classe II, 1ª divisão, esquelética, foi estudada em telerradiografias em norma lateral. O grupo experimental foi composto por 55 indivíduos brasileiros leucodermas, de ambos os gêneros, apresentando um ângulo ANB maior ou igual a 4.5 graus. A idade média foi 13.5 anos. Foram utilizadas grandezas cefalométricas da análise de Steiner e McNamara Jr. para avaliar a relação entre as posições angulares e lineares das bases apicais, estruturas dentárias e destas com as estruturas cranianas, comparando com os valores obtidos de um grupo controle (disponível na Faculdade de Odontologia de Bauru-USP). Os resultados mostraram que, no grupo experimental, a maxila apresentou-se bem posicionada em relação à base craniana. A relação maxilomandibular apresentou uma sobressaliência acentuada, o que já era previsível dado o critério de seleção da amostra experimental. A proporção geométrica entre as bases apicais apresentou a mandíbula de tamanho pequeno e a maxila normal. O padrão de crescimento craniofacial apresentou uma tendência vertical. Os incisivos superiores apresentaram-se inclinados para vestibular e bem posicionados pela avaliação linear. Os incisivos inferiores mostraram-se acentuadamente inclinados para vestibular e protruídos. Não houve diferença estatisticamente significante entre os gêneros

CONTROLE DA MICOTOXINA PATULINA POR RADIAÇÃO GAMA E ÓLEO ESSENCIAL DA NOZ MOSCADA (MYRISTICA FRAGRANS)

As micotoxinas são metabólitos secundários com variado grau de toxicidade e produzidos por diversos fungos. Por serem extremamente comuns e afetarem gêneros alimentícios em larga escala, a preocupação com sua ocorrência e com o desenvolvimento de métodos para descontaminação tem sido crescente em todo o mundo. Além disso, o pequeno conhecimento acerca de suas formas de ação e seu evidente potencial como agentes de guerra ressaltam a importância de maiores estudos na área. O presente trabalho teve por objetivo desenvolver uma metodologia para inativação da patulina, uma micotoxina produzida principalmente pelos gêneros Penicillium, Bissochlamys e Aspergillus, além de estratégias para evitar sua ocorrência. Foram utilizadas como ferramentas a irradiação gama para inativação e óleo essencial de noz moscada para controle da proliferação de cepas de fungos. Para análise dos resultados de inativação e composição das amostras de óleo essencial foram utilizadas a cromatografia líquida de alta eficiência e a cromatografia gasos

CONSTRUÇÃO PARTICIPATIVA DE ARRANJOS SILVIPASTORIS: UM ESTUDO DE CASO NO MUNICÍPIO DE SÃO BONIFÁCIO – SC

O presente estudo é uma reflexão sobre um trabalho desenvolvido com base em uma pesquisa participativa em sistemas agroflorestais, voltada a construção de arranjos silvipastoris no sistema de produção PRV (Pastoreio Racional Voisin), realizada com um grupo de agricultores familiares produtores de leite, no município de São Bonifácio/SC. A trabalho busca apreender o que os atores envolvidos – agricultores, técnicos,pesquisadores - entendem por participação, quais as características, potencialidades e dificuldades de um processo de pesquisa e extensão rural participativa. É um estudo de caráter qualitativo, cujos instrumentos foram a observação direta e entrevistas semi-estruturadas com atores-chave. Os dados foram analisados e interpretados segundo a metodologia “Discurso do Sujeito Coletivo” (DSC), que mostraram que o processo participativo ocorrido em São Bonifácio é entendido de diferentes formas pelos atores, evidenciando um conjunto de características que, ao mesmo tempo,potencializam este e outros processos de pesquisa e extensão rural participativa mas também representam grandes desafios

Rheology of enzyme liquefied corn stover slurries: The effect of solids concentration on yielding and flow behavior

The measurement of yield stress and shear thinning flow behavior of slurries formed from unpretreated corn stover at solids loadings of 100–300 g/L provides a key metric for the ability to move, pump, and mix this lignocellulosic slurry, particularly since corn stover slurries represent a major potential feedstock for biorefineries. This study compared static yield stress values and flow hysteresis of corn stover slurries of 100, 150, 200, 250, and 300 g/L, after these slurries were formed by adding pellets to a cellulase enzyme solution (Celluclast 1.5 L) in a fed-batch manner. A rotational rheometer was used to quantitate relative yield stress and its dependence on processing history at insoluble solids concentrations of 4%–21% (wt/vol). Key findings confirmed previous observations that yield stress increases with solids loadings and reaches ~3000 Pa at 25% (wt/vol) solids concentration compared to ~200 Pa after enzyme liquefaction. While optimization of slurry forming (i.e., liquefaction) conditions remains to be done, metrics for quantifying liquefaction extent are needed. The method for obtaining comparative metrics is demonstrated here and shows that the yield stress, shear thinning and shear thickening flow behaviors of enzyme liquefied corn stover slurries can be analyzed using a wide-gap rheometry setup with relative measuring geometries to mimic the conditions that may exist in a mixing vessel of a bioreactor while applying controlled and precise levels of strain