Revisiting the Phenomenon of Cellulase Action: Not All Endo- and Exo-Cellulase Interactions Are Synergistic

The conventional endo–exo synergism model has extensively been supported in literature, which is based on the perception that endoglucanases (EGs) expose or create accessible sites on the cellulose chain to facilitate the action of processive cellobiohydrolases (CBHs). However, there is a lack of information on why some bacterial and fungal CBHs and EGs do not exhibit synergism. Therefore, the present study evaluated and compared the synergistic relationships between cellulases from different microbial sources and provided insights into how different GH families govern synergism. The results showed that CmixA2 (a mixture of TlCel7A and CtCel5A) displayed the highest effect with BaCel5A (degree of synergy for reducing sugars and glucose of 1.47 and 1.41, respectively) in a protein mass ratio of 75–25%. No synergism was detected between CmixB1/B2 (as well as CmixC1/C2) and any of the EGs, and the combinations did not improve the overall cellulose hydrolysis. These findings further support the hypothesis that “not all endo-to exo-cellulase interactions are synergistic”, and that the extent of synergism is dependent on the composition of cellulase systems from various sources and their compatibility in the cellulase cocktail. This method of screening for maximal compatibility between exo- and endo-cellulases constitutes a critical step towards the design of improved synergistic cellulose-degrading cocktails for industrial-scale biomass degradation.

A Theoretical and Experimental Study on Esterification of Citric Acid with the Primary Alcohols and the Hydroxyl Groups of Cellulose Chain (n = 1-2) in Parched Condition

Esterification of citric acid (CA) with the primary alcohols and the hydroxyl groups of cellulose chain (n = 1-2) in parched condition were investigated by using density functional theory (DFT) method and a two-layer ONIOM approach. Geometry and energy of reactants, products, and transition state (TS) structures were optimized at B3LYP/6-311g (d, p) level and ONIOM (B3LYP/6-311g (d, p):PM3MM) level. The computational results show that the esterification occurs in the two main steps: the first step is the dehydration reaction of CA to form anhydrides of 5-membered ring and 6-membered ring and the second step is the ring opening reaction with the hydroxyl –OH groups to form the ester products. The energy barrier of dehydration reaction step is much higher than that of ring opening reaction step. Effect of substituent R in primary alcohol R-CH2OH (R: CH=CH2, CH2NHCH3, CH2OCH3, CH2Cl) and cellulose chain (1G, 2G) on the reactivity, which has negative inductive effect –I, is significant. The combination of calculation data and experiment data were applied to make findings more rigorous. The activation energy of CA was determined by using differential scanning calorimetry (DSC) and thermal gravimetric (TG) analysis to be E a exp = 47.8 kcal/mol; the experimental data favoured the dehydration reaction step of CA.

Silvicultura do eucalipto e a especialização do trabalho na cadeia produtiva de papel e celulose em Imperatriz-MA

O presente trabalho tem por objetivo analisar o processo de especialização produtiva do trabalho no Maranhão mediante o avanço da cadeia de papel e celulose em face da expansão e da intensificação da silvicultura do eucalipto desencadeada pela implantação da unidade fabril da Suzano Papel e Celulose no município de Imperatriz, sudoeste do estado do Maranhão. Dessa forma, busca-se questionar: há em curso uma especialização produtiva do trabalho nesse segmento, considerando trabalhadores com qualificação profissional de nível médio/técnico, em Imperatriz? Metodologicamente, além de revisão da literatura pertinente, utilizou-se, conjuntamente com pesquisas de campo, dados secundários sobre transformações no emprego local e nas qualificações profissionais locais advindas da implantação da Suzano. Os dados utilizados são originários da RAIS; CAGED; IBGE, além de escolas técnicas locais. Os resultados encontrados permitiram realizar mapeamento da cadeia de trabalho no segmento em destaque e verificar que há intenso e rápido aprofundamento da especialização produtiva do trabalho no setor de papel e celulose no estado. Abstract EUCALYPTUS SILVICULTURE AND THE SPECIALIZATION OF WORK IN THE PULP AND PAPER PRODUCTION CHAIN IN IMPERATRIZ - MA The main goal of this article is to study the labor specialization process in the state of Maranhão through the progress if the paper and cellulose chain over the expansion and reinforcement of the forestry from eucalyptus based on the implementation of the factory “Suzano Papel e Celulose” in Imperatriz, southwest of the Maranhão State. This drives the question: is there a movement to improve and specialize workers in this sector, taking into consideration not specialized or technical workers in the city of Imperatriz? For methodology it was used the book references, field research and secondary data about the changes in the way of work in the local plant and technical requirements for professional workers due to the implementation of “Suzano Papel e Celulose”. The data comes from “RAIS”; “CAGED”; “IBGE” and local technical schools. The results allow us to map the working group in the sector emphasizing that there is an intense and quick specialization regarding the work in this specific sector of paper and cellulose.

A biomathematical view on the fractional dynamics of cellulose degradation

We perform a biomathematical analysis of a model of cellulose degradation with derivative of fractional order γ. In the theory of biopolymers division, the phenomenon of shattering remains partially unexplained by classical models of clusters’ fragmentation. Thus, we first examine the case where the breakup rate H is independent of the size of the cellulose chain breaking up, following by the case where H is proportional to the size of the cellulose chain. Both cases show that the evolution of the biopolymer sizes distribution is governed by a combination of higher transcendental functions, namely the Mittag-Leffler function, the further generalized G-function and the Pochhammer polynomial. In particular, this shows existence of an eigen-property, that is, the system describing fractional cellulose degradation contains replicated and partially replicated fractional poles, whose effects are given by these functions.