RESUMO
Ethanol production by fermentation of lignocellulosic biomass-derived sugars involves a fairly ancient art and an ever-evolving science. Production of ethanol from lignocellulosic biomass is not avant-garde, and wood ethanol plants have been in existence since at least 1915. Most current ethanol production relies on starch- and sugar-based crops as the substrate; however, limitations of these materials and competing value for human and animal feeds is renewing interest in lignocellulose conversion. Herein, we describe methods for both simultaneous saccharification and fermentation (SSF) and a similar but separate process for partial saccharification and cofermentation (PSCF) of lignocellulosic biomass for ethanol production using yeasts or pentose-fermenting engineered bacteria. These methods are applicable for small-scale preliminary evaluations of ethanol production from a variety of biomass sources.
Assuntos
Biomassa , Etanol/síntese química , Fermentação/fisiologia , Lignina/metabolismo , Polissacarídeos/metabolismo , Ácidos/farmacologia , Reatores Biológicos , Biotecnologia/métodos , Biotransformação , Cromatografia Gasosa/métodos , Etanol/química , Etanol/metabolismo , Hidrólise , Modelos BiológicosRESUMO
Concerns for our environment and unease with our dependence on foreign oil have renewed interest in converting plant biomass into fuels and 'green' chemicals. The volume of plant matter available makes lignocellulose conversion desirable, although no single isolated organism has been shown to depolymerize lignocellulose and efficiently metabolize the resulting sugars into a specific product. This work reviews selected chemicals and fuels that can be produced from microbial fermentation of plant-derived cell-wall sugars and directed engineering for improvement of microbial biocatalysts. Lactic acid and ethanol production are highlighted, with a focus on engineered Escherichia coli.
Assuntos
Metabolismo dos Carboidratos , Etanol/metabolismo , Ácido Láctico/metabolismo , Plantas/metabolismo , Biomassa , Carboidratos/química , Escherichia coli/metabolismo , Etanol/química , Ácido Láctico/química , Modelos Biológicos , Estrutura Molecular , Pectinas/química , Pectinas/metabolismo , Desenvolvimento Vegetal , Polissacarídeos/química , Polissacarídeos/metabolismoRESUMO
Research is needed to allow more efficient processing of lignocellulose from abundant plant biomass resources for production to fuel ethanol at lower costs. Potential dedicated feedstock species vary in degrees of recalcitrance to ethanol processing. The standard dilute acid hydrolysis pretreatment followed by simultaneous sacharification and fermentation (SSF) was performed on leaf and stem material from three grasses: giant reed (Arundo donax L.), napiergrass (Pennisetum purpureum Schumach.), and bermudagrass (Cynodon spp). In a separate study, napiergrass, and bermudagrass whole samples were pretreated with esterase and cellulose before fermentation. Conversion via SSF was greatest with two bermudagrass cultivars (140 and 122 mg g(-1) of biomass) followed by leaves of two napiergrass genotypes (107 and 97 mg g(-1)) and two giant reed clones (109 and 85 mg g(-1)). Variability existed among bermudagrass cultivars for conversion to ethanol after esterase and cellulase treatments, with Tifton 85 (289 mg g) and Coastcross II (284 mg g(-1)) being superior to Coastal (247 mg g(-1)) and Tifton 44 (245 mg g(-1)). Results suggest that ethanol yields vary significantly for feedstocks by species and within species and that genetic breeding for improved feedstocks should be possible.
Assuntos
Etanol/metabolismo , Folhas de Planta/microbiologia , Caules de Planta/microbiologia , Poaceae/classificação , Poaceae/microbiologia , Saccharomyces cerevisiae/metabolismo , beta-Glucosidase/química , Folhas de Planta/química , Caules de Planta/química , Poaceae/química , Especificidade da EspécieRESUMO
Today's youth are at a disturbingly high risk for mental health and illness problems and are largely dissatisfied with the existing mental health services. Youth Net/Réseau Ado (YN/RA), supported by input from mental health professionals, is a bilingual mental health promotion program that seeks out the opinions and attitudes of youth regarding mental health and illness issues, while connecting them with appropriate resources and mental health services. This paper describes the Youth Net/Réseau Ado program and provides some guidelines for the identification of mental health and illness problems, including indicators of the risk of suicide.
Les adolescents d'aujourd'hui présentent un risque inquiétant de troubles psychologiques ou affectifs et se montrent très insatisfaits face aux services existants en santé mentale. Réseau ado/Youth Net (RA/YN), soutenu par l'apport des professionnels de la santé, est un programme bilingue de promotion de la santé mentale qui cherche à solliciter les opinions et les attitudes des adolescents au sujet de la santé mentale et des maladies s'y reliant, tout en orientant ceux-ci vers les ressources et les services pertinents. Cet article décrit le programme Réseau ado/Youth Net et contient des directives pour identifier les troubles de santé et de maladie mentale, y compris les indicateurs de risque de suicide.
