Second-Generation Ethanol: The Need is Becoming a Reality

Santos, Leandro Vieira dos; Carolina, de Barros GrassiMaria; Medina, GallardoJéssica Carolina; Pirolla, Renan Augusto Siqueira; Llerena, CalderónLuige; Vaz, de Carvalho-NettoOsmar; Parreiras, Lucas S.; Oliveira, CamargoEduardo Leal; Luzia, DrezzaAngela; Kazue, MissawaSílvia; Silva, TeixeiraGleidson; LunardiInes,; BressianiJosé,; Guimarães, PereiraGonçalo Amarante

doi:10.1089/ind.2015.0017

Cited by 107 publications

(103 citation statements)

References 81 publications

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“…Ethanol production from lignocellulosic biomass has attracted considerable research attention because of a growing realization of the energy crisis and climate change [1,2]. Rice straw (RS) is a by-product after rice grain collection.…”

Section: Introductionmentioning

confidence: 99%

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Structural Analysis of Alkaline Pretreated Rice Straw for Ethanol Production

Phitsuwan

Permsriburasuk

Baramee

et al. 2017

International Journal of Polymer Science

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Rice straw (RS) is an abundant, readily available agricultural waste, which shows promise as a potential feedstock for Asian ethanol production. To enhance release of glucose by enzymatic hydrolysis, RS was pretreated with aqueous ammonia (27% w/w) at two pretreatment temperatures: room temperature and 60 ∘ C. Statistical analysis indicated similarity of enzymatic glucose production at both pretreatment temperatures after 3-day incubation. Chemical composition, FTIR, and EDX analyses confirmed the retention of glucan and xylan in the pretreated solid, but significant reduction of lignin (60.7% removal) and silica. SEM analysis showed the disorganized surfaces and porosity of the pretreated RS fibers, thus improving cellulose accessibility for cellulase. The crystallinity index increased from 40.5 to 52.3%, indicating the higher exposure of cellulose. With 10% (w/v) solid loadings of pretreated RS, simultaneous saccharification and fermentation yielded a final ethanol concentration of 24.6 g/L, corresponding to 98% of maximum theoretical yield. Taken together, aqueous ammonia pretreatment is an effective method to generate highly digestible pretreated RS for bioethanol production and demonstrates potential application in biorefinery industry.

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Section: Introductionmentioning

confidence: 99%

“…Production of sugars from RS by enzymatic reaction is of industrial interest because of mild-reaction conditions used and relatively pure product formation [1,5]. However, 2 International Journal of Polymer Science in bioethanol industry, the efficient utilization of lignocellulosic biomass is limited by its recalcitrant nature [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Structural Analysis of Alkaline Pretreated Rice Straw for Ethanol Production

Phitsuwan

Permsriburasuk

Baramee

et al. 2017

International Journal of Polymer Science

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“…With this production increase, second-generation ethanol has become a promising alternative for overcoming challenges such as high production costs and acreage limitation (Santos et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Comparison between different selection indices in energy cane breeding

Azeredo¹,

Bhering²,

Brasileiro³

et al. 2017

Genet. Mol. Res.

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ABSTRACT. Sugarcane breeding programs have been adapting to a new market demand: aside from high sucrose yield per hectare, the sector needs new cultivars with higher fiber percentages. The selection of sugarcane clones based on phenotype alone is a complex task. The selected clones should display high performance in a series of yieldand quality-related traits. Selection indices can provide information about which clones can best combine the traits of agronomic interest. In this study, different selection indices were evaluated in a population of 220 clones. The following traits were evaluated: weight of 10 stalks with straw, weight of 10 stalks with no straw, tons of cane per hectare with straw, tons of cane per hectare with no straw, sucrose content, fiber percentage, and tons of fiber per hectare. The selection indices of Smith (1936) and Hazel (1943) and Mulamba and Mock (1978), the base index (Williams, 1962), and the index of Pesek and Baker (1969) were used. The selection index of Mulamba and Mock (1978) without economic weight estimates, the index of Mulamba and Mock with economic weights based on heritability, and the index of Pesek and Baker (1969) with the desired gains based on genetic standard deviations were efficient for the selection of energy cane clones with good fiber yield, sucrose content, and tons of cane per hectare.

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“…Bioethanol has been touted as a cleaner and renewable alternative to replace fossil fuels and reduce carbon emissions5. In Brazil, first-generation ethanol is produced from the fermentation of sucrose-rich sugarcane extract, using a process in which Saccharomyces cerevisiae yeast cells are continuously recycled through successive batches, in some cases for up to 250 days in a row6.…”

mentioning

confidence: 99%

“…A major challenge to the establishment of second-generation operations is the availability of biocatalysts able to metabolize the five-carbon (C5) sugar xylose derived from the hydrolysis of lignocellulosic biomass feedstocks5. S. cerevisiae is normally unable to metabolize xylose, but two pathways have been commonly used to engineer this activity into yeast cells1011.…”

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confidence: 99%

Unraveling the genetic basis of xylose consumption in engineered Saccharomyces cerevisiae strains

Santos

Carazzolle

Nagamatsu

et al. 2016

Sci Rep

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The development of biocatalysts capable of fermenting xylose, a five-carbon sugar abundant in lignocellulosic biomass, is a key step to achieve a viable production of second-generation ethanol. In this work, a robust industrial strain of Saccharomyces cerevisiae was modified by the addition of essential genes for pentose metabolism. Subsequently, taken through cycles of adaptive evolution with selection for optimal xylose utilization, strains could efficiently convert xylose to ethanol with a yield of about 0.46 g ethanol/g xylose. Though evolved independently, two strains carried shared mutations: amplification of the xylose isomerase gene and inactivation of ISU1, a gene encoding a scaffold protein involved in the assembly of iron-sulfur clusters. In addition, one of evolved strains carried a mutation in SSK2, a member of MAPKKK signaling pathway. In validation experiments, mutating ISU1 or SSK2 improved the ability to metabolize xylose of yeast cells without adaptive evolution, suggesting that these genes are key players in a regulatory network for xylose fermentation. Furthermore, addition of iron ion to the growth media improved xylose fermentation even by non-evolved cells. Our results provide promising new targets for metabolic engineering of C5-yeasts and point to iron as a potential new additive for improvement of second-generation ethanol production.

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Second-Generation Ethanol: The Need is Becoming a Reality

Cited by 107 publications

References 81 publications

Structural Analysis of Alkaline Pretreated Rice Straw for Ethanol Production

Structural Analysis of Alkaline Pretreated Rice Straw for Ethanol Production

Comparison between different selection indices in energy cane breeding

Unraveling the genetic basis of xylose consumption in engineered Saccharomyces cerevisiae strains

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