News and Trends
An international group of scientists (from Sweden, Denmark and Portugal) reported the use of "evolutionary engineering" to improve the metabolic versatility of a strain of Saccharomyces cerevisiae, to effectively utilize mixed-pentoses for ethanol fermentation. Saccharomyces cerevisiae is the yeast that is commonly used for traditional fermentation of ethanol from glucose (a six-carbon sugar, or "hexose"). However, this yeast does not have a built-in metabolic capability to effectively utilize mixed-pentoses (5-carbon sugars, such as xylose and arabinose), which is abundantly present in lignocellulosic biomass after pretreatment. For such, it must be endowed with a metabolic versatility to utilize both hexoses and mixed-pentoses to ethanol. This would do much to increase "cellulose-ethanol" productivity and lower production cost.
The international scientific group was able to obtain an "evolved" strain of Saccharomyces cerevisiae with this metabolic versatility by using the tools of "evolutionary molecular biology". Also called, "evolutionary engineering", the technique reportedly "mimics" the process of natural evolution in living organisms (i.e. the "emergence of the best" from descendants), for obtaining desired biological traits. There are generally two steps in the technique: (1) the introduction of random mutations into a target gene to generate the variation, and (2) selection of the mutated genes that express products with a desired property under selective pressure. In the study, the scientists used a continuous culture technique under substrate limitation of xylose and arabinose, to implement selective pressure. Results showed that the evolved strain had increased consumption rates of the mixed-pentoses (xylose and arabinose), as well as an increase in the levels of pentose-utilization-associated enzyme activities. The full report is published in the open-access journal, Biotechnology for Biofuels (URL above).
Related information on evolutionary engineering:
Findings from the United Nations Food and Agriculture Organization (UN-FAO) Bioenergy and Food Security (BEFS) Project indicate that "Thailand has the means to realize the Government's plan for the development of the biofuels industry in a sustainable manner, without negatively impacting on food security". The roadmap for biofuels development program of Thailand is embodied in the "Thai Alternative Energy Development Plan", which aims to expand biofuels production to 5 billion liters by 2022. In order to achieve the targets, "total cassava production will need to grow 25 percent from 31.5 million tonnes in 2010 to over 40 million tonnes by 2022 largely through yield improvements. Production of crude palm oil is expected to double from 1.8 million tonnes to 3.4 millions tonnes over the same period following expansion of oil palm plantations".
The findings of the FAO-BEFS project were presented recently at a high-level forum, co-hosted by the Office of the National Economic and Social Development Board and FAO in Bangkok. Among the highlights of the findings are: (1) "Biofuels production in Thailand is already economically competitive and offers measurable greenhouse advantages over fossil transport fuels", (2) better farm productivity will bring benefits to Thailand's biofuel sector in terms of increased farm incomes, and reduction of greenhouse gas emissions; but in order to ensure sustainability of biofuels production, "significant land or crop use changes in feedstock production must be avoided and biofuel producers should continue to identify opportunities to utilize renewable sources and wastes in the production process", (3) "agricultural research and extension need to be further promoted, in particular associated to plant pest management, land and water use efficiency, varietal improvements, plant nutrient and soil fertility", (4) the North-east region of Thailand was identified as the target area where substantial investments in agricultural productivity will be needed.
Energy Crops and Feedstocks for Biofuels Production
Researchers from the Universidad Rey Juan Carlos and the Universidad de Murcia (both in Spain) report a process for the production of biodiesel by direct transesterification of fermentation cultures of an oleaginous (oil-bearing) fungus, Mucor circinelloides . The common process for biodiesel production usually involves the following steps: (1) cultivation of the (biomass) feedstock, (2) extraction of oil from the biomass, and (3) chemical transformation of the (extracted) oil into biodiesel by a transesterification reaction. Until recently, seed oils and oleaginous algae were the more popular biodiesel feedstocks.
Lately, there is growing interest in other potential feedstocks, such as oleaginous fungi. Among the advantages of oleaginous microorganisms (over plant-based feedstocks such as Jatropha) are: (1) the oils from oleaginous microorganisms have "ideal lipid profiles" for biodiesel production, and (2) oleaginous microorganisms are more amenable to genetic manipulation for further improvement of lipid profiles. In the present study, the researchers report the "direct" production of biodiesel from submerged (fermentation) cultures of Mucor circinelloides, by direct transesterification, without the need for extracting the oil from the biomass. The elimination of an oil extraction step could translate to lower cost of production. The "analyzed properties of the M. circinelloides-derived biodiesel using three different catalysts (BF3, H2SO4, and HCl) fulfilled the specifications established by the American standards and most of the European standard specifications". The full paper is published in the journal, Energy and Fuels (URL above).
Researchers from the Michigan State University (United States), Zhejiang Forestry University (China), and Indian Institute of Technology-Madras (India) investigated a process for bioethanol production from starch-rich lignocellulosic feedstocks. The corn-grain constitutes the starch-rich component of the crop, while the stalks, stem, and leaves ("stover") constitute the cellulosic part of the crop. Although corn is usually harvested by separating the grain from the stover, (and then separately processed into ethanol), the harvest of whole corn plants (grain plus stover) for subsequent ethanol processing by co-hydrolysis, represents an alternative. In the study, the researchers used mature whole corn plants and corn silage as the test feedstock. They subjected the material to a thermochemical pretreatment by ammona fiber expansion (AFEX), followed by co-hydrolysis by the enzymes amylase (starch hydrolysis) and cellulase (cellulose hydrolysis). Enzymatic digestibility and ethanol fermentability were evaluated after pretreatment and co-hydrolysis. The results showed that AFEX-pretreated starch-rich substrates had a 1.5-fold to 3.5-fold higher enzymatic hydrolysis compared to untreated (no AFEX pretreatment) substrates. "Sequential addition of cellulase after the hydrolysis of starch (by amylase) within whole corn plants resulted in 15% to 20% higher hydrolysis compared to simultaneous addition of both (amylase and cellulase) enzymes. Ethanol concentrations after fermentation were 28 g/L and 30 g/L, for corn silage and whole corn plants, respectively. The complete results are published in the open access journal, Biotechnology for Biofuels (URL above).
Related information of corn silage: http://www.utextension.utk.edu/publications/spfiles/sp434d.pdf
Biofuels Policy and Economics
In an effort to ensure that all biofuels (produced and imported by EU member countries) are products of sustainable practices, the European Commission (EC) recently set up a scheme for the certification of sustainable biofuels. The scheme is embodied by two Communication documents and one Decision document. The highlights of the scheme (as reported by the EC press release) are: "(1) Sustainable Biofuel Certificates: The Commission encourages industry, governments and NGOs to set up "voluntary schemes" to certify biofuel sustainability – and explains the standards these must meet to gain EU recognition. One of the main criteria is that they have independent auditors who check the whole production chain, from the farmer and the mill, via the trader, to the fuel supplier who delivers petrol or diesel to the filling station. The Communication sets standards requiring this auditing to be reliable and fraud-resistant; (2) Protecting untouched nature: The Communication explains that biofuels should not be made from raw materials from tropical forests or recently deforested areas, drained peatland, wetland or highly biodiverse areas – and how this should be assessed. It makes clear that the conversion of a forest to a palm oil plantation would fall foul of the sustainability requirements; and (3) Promote only biofuels with high greenhouse gas savings. The Communication reiterates that Member States have to meet binding, national targets for renewable energy and that only those biofuels with high greenhouse gas savings count for the national targets, explaining also how this is calculated. Biofuels must deliver greenhouse gas savings of at least 35% compared to fossil fuels, rising to 50% in 2017 and to 60%, for biofuels from new plants, in 2018.
The United States Department of Agriculture-Economic Research Service (USDA-ERS) recently released a report on the "short-term outlook for production of next-generation biofuels and the near-term challenges facing the sector". Next-generation biofuels are made from advanced technologies that utilize an expanded range of non-traditional feedstocks. Among the highlights of the report are: (1) public sector support for next-generation biofuels is driven by national interest for energy independence with food security, mitigation of greenhouse gas emissions, and enhancement of rural employment opportunities; and (2) the key challenges facing next-generation biofuels are: the reduction of high capital and production costs, availability of financial support during pre-commercial development, establishment of feedstock supply arrangements, and overcoming blend wall constraints. The full report can be accessed from the USDA-ERS website (URL above).