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High gravity and high cell density mitigate some of the fermentation inhibitory effects of softwood hydrolysates
Nuwan Sella Kapu, Maya Piddocke and Jack (John) N Saddler
AMB Express , 2013, DOI: 10.1186/2191-0855-3-15
Abstract: After steam pretreatment of lignocellulosic substrates the fermentation of the biomass derived sugars to ethanol is typically problematic because of both the generally low sugar concentrations that can be supplied and the presence of naturally occurring and process derived inhibitors. As the majority of the inhibitory materials are usually associated with the hemicellulose rich, water soluble component, this fraction was supplemented with glucose to simulate high solids, un-detoxified substrate to see if a high gravity/high cell consistency approach might better cope with inhibition. Several yeast strains were assessed, with the Tembec T1, T2 and Lallemand LYCC 6469 strains showing the greatest ethanol productivity and yield. The addition of supplemental glucose enabled the faster and quantitatively higher removal of hydroxymethylfurfural (HMF). High cell density could provide effective fermentation at high sugar concentrations while enhancing inhibitor reduction. A 77% ethanol yield could be achieved using strain LYCC 6469 after 48 h at high cell density. It was apparent that a high cell density approach improved ethanol production by all of the evaluated yeast strains.
Access to cellulose limits the efficiency of enzymatic hydrolysis: the role of amorphogenesis
Valdeir Arantes, Jack N Saddler
Biotechnology for Biofuels , 2010, DOI: 10.1186/1754-6834-3-4
Abstract: Continuing interest in the utilization of renewable biomass resources for the production of alternative fuels has brought increasing attention on the technical bottlenecks that still need to be resolved and how the variability of different lignocellulosic materials might influence the efficiency of enzymatic hydrolysis.Over the past 40 to 50 years, many excellent research groups have been assessing the ability of carbohydrate-degrading enzymes to depolymerize the cellulosic component of lignocellulosic substrates into soluble, fermentable sugars. However the efficient, rapid and complete enzymatic hydrolysis of lignocellulosic materials using low protein loadings has proven to be one of the major technical and economical bottlenecks in the overall bioconversion process of lignocellulose to biofuels [1-4].Several factors related to the substrates (such as lignin/hemicellulose association, degree of cellulose crystallinity and polymerization, extent of surface area) and enzymes (such as end-product inhibition, need for synergism, irreversible enzyme adsorption) have been suggested to account for the recalcitrance of cellulose to enzymatic hydrolysis [5]. However, there is still considerable disagreement in the literature regarding the relative importance of each of these factors, and our understanding of how enzymes completely hydrolyze cellulose is still far from complete.Enzymatic saccharification of cellulose is generally described as a heterogeneous reaction system in which cellulases in an aqueous environment react with the insoluble, macroscopic and structured cellulose, containing highly ordered and less ordered regions. Unsatisfactorily, the majority of the research directed at understanding the mechanisms of cellulose biodegradation has given little attention to the existence and the influence that the fibrillar architecture of the cellulose fibril network will have on the enzyme reactivity and consequential course of heterogeneous cellulase reactions.In orde
Cellulose accessibility limits the effectiveness of minimum cellulase loading on the efficient hydrolysis of pretreated lignocellulosic substrates
Valdeir Arantes, Jack N Saddler
Biotechnology for Biofuels , 2011, DOI: 10.1186/1754-6834-4-3
Abstract: Bioethanol derived from the bioconversion of lignocellulosic feedstocks continues to attract global interest as a potentially environmentally compatible alternative to current petroleum-based transportation fuels. However, considerable technical improvements are still needed before efficient and economically feasible lignocellulosic biomass-based bioethanol processes can be commercialized. One of the major limitations of this process is the consistently high cost of the enzymes involved in the conversion of the cellulose component into fermentable sugars [1]. This is primarily due to the comparatively high (compared with amylase loadings required for starch hydrolysis) protein loadings commonly required to overcome the substrate features and enzyme-related factors limiting effective cellulose hydrolysis [2]. Achieving rapid and complete enzymatic hydrolysis of lignocellulosic biomass at low protein loadings continues to be a major technical challenge in the commercialization of cellulose-based processes converting biomass to ethanol.In a typical batch enzyme-based process, cellulose conversion-time experiments are characterized by a three-phase curve (Figure 1A). This usually starts with the rapid adsorption of the cellulases onto the readily accessible cellulose, followed by an initial, fast rate of hydrolysis. However, the reaction quickly reaches an intermediate phase, characterized by a moderate hydrolysis reaction rate when about 50-70% of the original substrate has been hydrolyzed. Thereafter, a very slow phase is characterized by a steady decrease of the reaction rate, which results in only a slight increase in the conversion of the remaining (the so-called 'inaccessible' or recalcitrant) cellulose. Typically, extended hydrolysis times and/or high protein loadings are required to achieve a near-complete conversion of cellulose (Figure 1B). In some cases, depending on the nature of the substrate and the pretreatment method used, even at very high protein loadi
Effect of replacing polyol by organosolv and kraft lignin on the property and structure of rigid polyurethane foam
Pan Xuejun,Saddler Jack N
Biotechnology for Biofuels , 2013, DOI: 10.1186/1754-6834-6-12
Abstract: Background Lignin is one of the three major components in plant cell walls, and it can be isolated (dissolved) from the cell wall in pretreatment or chemical pulping. However, there is a lack of high-value applications for lignin, and the commonest proposal for lignin is power and steam generation through combustion. Organosolv ethanol process is one of the effective pretreatment methods for woody biomass for cellulosic ethanol production, and kraft process is a dominant chemical pulping method in paper industry. In the present research, the lignins from organosolv pretreatment and kraft pulping were evaluated to replace polyol for producing rigid polyurethane foams (RPFs). Results Petroleum-based polyol was replaced with hardwood ethanol organosolv lignin (HEL) or hardwood kraft lignin (HKL) from 25% to 70% (molar percentage) in preparing rigid polyurethane foam. The prepared foams contained 12-36% (w/w) HEL or 9-28% (w/w) HKL. The density, compressive strength, and cellular structure of the prepared foams were investigated and compared. Chain extenders were used to improve the properties of the RPFs. Conclusions It was found that lignin was chemically crosslinked not just physically trapped in the rigid polyurethane foams. The lignin-containing foams had comparable structure and strength up to 25-30% (w/w) HEL or 19-23% (w/w) HKL addition. The results indicated that HEL performed much better in RPFs and could replace more polyol at the same strength than HKL because the former had a better miscibility with the polyol than the latter. Chain extender such as butanediol could improve the strength of lignin-containing RPFs.
The enhancement of enzymatic hydrolysis of lignocellulosic substrates by the addition of accessory enzymes such as xylanase: is it an additive or synergistic effect?
Jinguang Hu, Valdeir Arantes, Jack N Saddler
Biotechnology for Biofuels , 2011, DOI: 10.1186/1754-6834-4-36
Abstract: The reported work assessed the interaction between cellulase and xylanase enzymes and their potential to improve the hydrolysis efficiency of various pretreated lignocellulosic substrates when added at low protein loadings. When xylanases were added to the minimum amount of cellulase enzymes required to achieve 70% cellulose hydrolysis of steam pretreated corn stover (SPCS), or used to partially replace the equivalent cellulase dose, both approaches resulted in enhanced enzymatic hydrolysis. However, the xylanase supplementation approach increased the total protein loading required to achieve significant improvements in hydrolysis (an additive effect), whereas the partial replacement of cellulases with xylanase resulted in similar improvements in hydrolysis without increasing enzyme loading (a synergistic effect). The enhancement resulting from xylanase-aided synergism was higher when enzymes were added simultaneously at the beginning of hydrolysis. This co-hydrolysis of the xylan also influenced the gross fiber characteristics (for example, fiber swelling) resulting in increased accessibility of the cellulose to the cellulase enzymes. These apparent increases in accessibility enhanced the steam pretreated corn stover digestibility, resulting in three times faster cellulose and xylan hydrolysis, a seven-fold decrease in cellulase loading and a significant increase in the hydrolysis performance of the optimized enzyme mixture. When a similar xylanase-aided enhancement strategy was assessed on other pretreated lignocellulosic substrates, equivalent increases in hydrolysis efficiency were also observed.It was apparent that the 'blocking effect' of xylan was one of the major mechanisms that limited the accessibility of the cellulase enzymes to the cellulose. However, the synergistic interaction of the xylanase and cellulase enzymes was also shown to significantly improve cellulose accessibility through increasing fiber swelling and fiber porosity and also plays a major
Use of substructure-specific carbohydrate binding modules to track changes in cellulose accessibility and surface morphology during the amorphogenesis step of enzymatic hydrolysis
Gourlay Keith,Arantes Valdeir,Saddler Jack N
Biotechnology for Biofuels , 2012, DOI: 10.1186/1754-6834-5-51
Abstract: Background Cellulose amorphogenesis, described as the non-hydrolytic “opening up” or disruption of a cellulosic substrate, is becoming increasingly recognized as one of the key steps in the enzymatic deconstruction of cellulosic biomass when used as a feedstock for fuels and chemicals production. Although this process is thought to play a major role in facilitating hydrolysis, the lack of quantitative techniques capable of accurately describing the molecular-level changes occurring in the substrate during amorphogenesis has hindered our understanding of this process. Results In this work, techniques for measuring changes in cellulose accessibility are reviewed and a new quantitative assay method is described. Carbohydrate binding modules (CBMs) with specific affinities for crystalline (CBM2a) or amorphous (CBM44) cellulose were used to track specific changes in the surface morphology of cotton fibres during amorphogenesis. The extents of phosphoric acid-induced and Swollenin-induced changes to cellulose accessibility were successfully quantified using this technique. Conclusions The adsorption of substructure-specific CBMs can be used to accurately quantify the extent of changes to cellulose accessibility induced by non-hydrolytic disruptive proteins. The technique provided a quick, accurate and quantitative measure of the accessibility of cellulosic substrates. Expanding the range of CBMs used for adsorption studies to include those specific for such compounds as xylan or mannan should also allow for the accurate quantitative tracking of the accessibility of these and other polymers within the lignocellulosic biomass matrix.
Special Issue from the NSERC Bioconversion network workshop: pretreatment and fractionation of biomass for biorefinery/biofuels
Saddler Jack,Kumar Linoj
Biotechnology for Biofuels , 2013, DOI: 10.1186/1754-6834-6-17
Abstract:
Self-Directed Learners or Not? Delivering Agroforestry Technology to Farmers in the Philippines  [PDF]
Jack Baynes, John Herbohn
Open Journal of Forestry (OJF) , 2011, DOI: 10.4236/ojf.2011.11001
Abstract: This paper presents an evaluation of the usefulness of a participatory approach and adult learning principles for agroforestry extension in the Philippines. Visual observations and analysis of interviews with farmers during an extension program found that their ability to act as self-directed adult learners changed according to the situations with which they were faced. Farmers used a self-directed approach to their selection of inputs for the establishment of woodlots. However, when propagating seedlings, lack of technical knowledge caused them to shift to a state of dependency on ‘top-down’ didactic instruction. Farmers’ familiarity with agricultural crops, e.g. rice and coconuts, did not provide them with the skills to raise tree seedlings. A consequence of farmers applying their own interpretation of woodlot establishment procedures was that some sites were destroyed and seedling growth on other sites was poor. These failed woodlots are likely to present a negative image of the program in the future. Contributing influences to farmers’ limited uptake of technology may have been a lack of other sources of support and information and the difficulty of interacting and sharing ideas with their peers. The practical implications of this research are that farmers in developing countries may lack the education, support services and peer-to-peer interaction to behave similarly to self-directed learners in developed countries. A totally participatory approach to program delivery may maintain participants’ enthusiasm and commitment but may result in unforseen outcomes. Hence, a flexible approach to the use of adult learning principles may be necessary.
APLICACIONES DE LOS SISTEMAS DE INFORMACIóN GEOGRáFICA Y SENSORES REMOTOS AL MANEJO DE PESQUERíAS MARINAS Y DESAFíOS PARA SU DESARROLLO EN COLOMBIA
Selvaraj,John J.; Rajasekharan,Maya; Guzmán-Alvis,ángela I.;
Boletín de Investigaciones Marinas y Costeras - INVEMAR , 2009,
Abstract: geographic information system (gis) and remote sensing (rs) techniques have been used increasingly for marine fisheries development and management over the last years. however, its applications continue to be scarce in colombia. this paper briefly reviews use of spatial tools in marine fisheries management, both retrospectively and predictively. case studies of rs and gis in fisheries research in colombia and challenges for future use for management measures are discussed. in order to harness the potential of gis and rs tools in marine fisheries research and management, priority should be given for training fisheries scientists in rs and gis, increasing collaboration among institutions, departments, standardize data collection, and development of a common platform for data sharing.
Características clínicas y microbiológicas de los pacientes neutropénicos febriles con neoplasias hematológicas
Octavio Germán Mu？oz Maya,Ana María Rodelo Vélez,John Jaime Carvajal,Javier Mauricio González
Iatreia , 2008,
Abstract: Se estudiaron en forma retrospectiva 441 historias clínicas en el período comprendido entre enero de 2003 y diciembre de 2005. De éstas, se identificaron las características de 117 episodios de neutropenia febril en 96 pacientes. La mediana de edad fue 34 a os y el 56,4% de los episodios ocurrieron en hombres. Las más frecuentes neoplasias hematológicas relacionadas con neutropenia febril fueron leucemia linfoide aguda (LLA) y leucemia mieloide aguda (LMA) con 45 episodios de cada una, que corresponden al 76,9%. La mediana de duración de la neutropenia fue 8 días y el 60,7% de los casos entraron en la categoría de neutropenia grave. La mortalidad global fue del 32% y el 81,5% de estas muertes estuvieron asociadas directamente con la infección. Se obtuvo aislamiento microbiológico en el 51% de los eventos. Los bacilos gram negativos (BGN) constituyeron el 59% de los aislamientos microbiológicos y los cocos gram positivos el 32%. El 14,3% de los BGN aislados fueron positivos para beta lactamasas de espectro extendido (BLEE) y la resistencia global a ciprofloxacina alcanzó el 31,4%. El esquema antimicrobiano empírico más frecuentemente utilizado fue ciprofloxacina más ceftriaxona; la respuesta terapéutica fue desfavorable en 65% de los casos. En el Hospital San Vicente de Paúl de Medellín siguen primando los gérmenes gram negativos y son altas las tasas de resistencia a los antibióticos utilizados tradicionalmente como de primera línea, lo que sugiere la necesidad de reevaluar la pertinencia de estos esquemas.
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