Consolidating the Feedstock Crops Cellulosic Biodiesel with Cellulosic Bioethanol Technologies: A Biotechnology Approach

Mariam Sticklen*
Department of Crop, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48823, USA
Corresponding Author :	Mariam Sticklen Department of Crop, Soil and Microbial Sciences Michigan State University, East Lansing, MI 48823 USA Tel: 1+517-355-0271 E-mail: Stickle1@msu.edu
Received October 07, 2015; Accepted October 09, 2015; Published October 15, 2015
Citation: Sticklen M (2015) Consolidating the Feedstock Crops Cellulosic Biodiesel with Cellulosic Bioethanol Technologies: A Biotechnology Approach. Adv Crop Sci Tech 3:e133. doi:10.4172/2329-8863.1000e133
Copyright: © 2015 Sticklen M. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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At present, the US is the largest producer of bioethanol (i.e. ethanol mostly produced from corn seed starch), and biodiesel (i.e. oil produced from oil seed crops). Considering controversies around whether governments should allow the conversions of food and feed into fuels or should they put a limit on such conversions, the future market potentials for crop vegetative wastes cellulosic bioethanol and cellulosic biodiesel is enormous.

The majority of crop lipids are in the seeds of oil seed crops. In certain cases such as in palm oil and olive trees, the majority of lipids are in the crop fruit. Lipids also exist in crop vegetative tissues including leaves, stems and husks. However, lipids of the vegetative tissues are at very low levels and mostly are in cell membranes and outside of the leaf epidermis in form of wax. For example, the lipids per dry weight of oil seeds and oil fruits could be as high as ~80-90%, while the vegetative tissues of normally contain less than 2-3% lipids. A couple of most recent review articles [1,2] show that it is possible to increase the lipid contents of plants vegetative tissues via metabolic engineering. A couple of other scientific teams were recently able to produce high quantities (9.5 to 17% per dry matter) of high density oil in form of triacylglyceride (TAG) in sugarcane [3] and tobacco (Nicotiana tobacum) [4] leaves. The author’s team also recently developed 3rd generation of metabolically engineered maize plants that are producing abundant oil droplets in their leaf cells (unpublished data). It is also possible to shift the fatty acid contents of cellulosic oil from biodiesel oil to vegetable oil by overexpressing of certain genes that are associated with lipid biosynthesis [5]. The overexpression of certain other genes associated with lipid biosynthesis can result in productions of unusual fatty acids such as epoxy fatty acids [6], and fatty acids of acyl triglycerides [7], or can result in a shift of fatty acids from one type to another [8]. Therefore, it is expected that biodiesel can be produced in crops vegetative biomass for extraction and use, and its fatty acid content be modified as might become needed.

On the other hands, cellulosic ethanol is produced through the use of microbial cellulases that convert crop cellulose into fermentable sugars and via pretreatment processes that either breakdown or remove the lignin component of lignocellulosic biomass to allow the exposure of cellulose of the lignocellulosic matter to cellulase enzymes. However, production of microbial cellulases and pretreatment processes of lignocellulosic matter are very expensive. To cut the costs of production of cellulosic ethanol, microbial heterologous cellulases have been produced within the crop vegetative biomass, specifically inside crops vegetative biomass sub-cellular compartments, including the apoplast (i.e. the free space outside of the plasma membrane and the cell wall) [5], chloroplast [6], vacuole [7] and mitochondria [8] or within multiple number of sub-cellular compartments [9,10]. In addition, lignin of crop vegetative biomass has been reduced via the RNA interference (RNAi) technology [11] and the lignin structure has been changed in a manner that it can be broken down easily with minimum needs for pretreatment processes [12].

This Editor believes that it must be possible to produce high density lipids as biodiesel via metabolic engineering, extract the biodiesel oil and then convert the lignocellulosic residues into cellulosic ethanol. In fact the two biofuels production systems are well compatible with the existing cellulosic ethanol refinery. Such integrated technology can contribute towards replacing of the environmentally harmful and nonrenewable petroleum fuel to cellulosic biofuels without replacing of the food or feed for fuels. Technologies associated with cellulosic biofuels are not difficult and could be used around the globe especially in countries where abundant crop residues such as rice straws are burned to waste, creating environmental contaminations and human health problems including asthma.

References

References

1. value="1" id="Reference_Titile_Link">Chapman KD, Ohlrogge JB(2012) Compartmentation of Triacylglycerol Accumulation in Plants. J BiolChem287:2288-2294.


2. value="2" id="Reference_Titile_Link">Hardwood JL (2014) Inspired by Lipids. E.J. Lipid Science and Technology 16:1259-1267.


3. value="3" id="Reference_Titile_Link">Zale J, Jung JH, Kim JY, Pathak B, Karan R, et al.(2015) Metabolic engineering of sugarcane to accumulate energy-dense triacylglycerols in vegetative biomass. Plant Biotech J 1-9.


4. value="4" id="Reference_Titile_Link">Vanhercke T, El Tahchy A, Liu Q, X-Rong Zhou, Shrestha P, et al. (2014) Metabolic engineering of biomass for high energy density: oilseed-like triacylglycerol yields from plant leaves. Plant Biotechnol J 12: 231-239.


5. value="5" id="Reference_Titile_Link">Andrianov V, Borisjuk N, Pogrebnyak N, Brinker A, Dixon J, et al. (2010) Tobacco as a production platform for biofuel: overexpression of Arabidopsis DGAT and LEC2 genes increases accumulation and shifts the composition of lipids in green biomass. Plant Biotechnol J 8:277-287.


6. value="6" id="Reference_Titile_Link">Li R, Yu K, Wu Y, Tateno M, Hatanaka T, et al. (2012) Vernonia DGATs can complement the disrupted oil and protein metabolism in epoxygenase-expressing soybean seeds. Metabolic Eng 14:29-38.


7. value="7" id="Reference_Titile_Link">Bates PD,Johnsonb SR, Caoc X, Lid J, Namd JD et al. (2014)Fatty acid synthesis is inhibited by inefficient utilization of unusual fatty acids for glycerolipid assembly. PANS 111:1204–1209.


8. value="8" id="Reference_Titile_Link">Vanhercke T, El Tahchy A, Shrestha P, Zhou XR, Singh SP, et al. (2013) Synergistic effect of WRI1 and DGAT1 coexpression on triacylglycerol biosynthesis in plants. FEBS Lett 587:364–369.


9. value="9" id="Reference_Titile_Link">Badhan A, Jin L, Wang Y, Han S, Kowalczys K, et al. (2014) Expression of a fungal ferulic acid esterase in alfalfa modifies cell wall digestibility. Biotechnology for Biofuels 7:39.


10. value="10" id="Reference_Titile_Link">Hahn S, Giritch A, Bartels D, Bortesi L, Gleba Y (2015) A novel and fully scalable Agrobacterium spray-based process for manufacturing cellulases and other cost-sensitive proteins in plants. Plant Biotechnol J 13:708-16.


11. value="11" id="Reference_Titile_Link">Harrison M, Zhang ZY, Shand K, Chong B, Nichols J, et al. (2014a) The combination of plant-expressed cellobiohydrolase and low dosages of cellulases for the hydrolysis of sugar cane bagasse. Biotechnology for Biofuels 7: 131.


12. value="12" id="Reference_Titile_Link">Mei CS, Park SH, Sabzikar R, Ransom C, Qi CF, et al. (2009) Green tissue-specific production of a microbial endo-cellulase in maize (Zea mays L.) endoplasmic-reticulum and mitochondria converts cellulose into fermentable sugars. J Chem Technol Biot 84: 689-695.


13. value="13" id="Reference_Titile_Link">Voges MJ, Silver PA, Way JC, Mattozzi MD (2013) Targeting a heterologous protein to multiple plant organelles via rationally designed 5′ mRNA tags. J Biol Eng 7: 20.


14. value="14" id="Reference_Titile_Link">Park SH, Ransom C, Mei CS, Sabzikar R, Qi CF,,et al. (2011) The quest for alternatives to microbial cellulase mix production: corn stover-produced heterologous multi-cellulases readily deconstruct lignocellulosic biomass into fermentable sugars. J Chem Technol Biotechnol 86: 633-641.


15. value="15" id="Reference_Titile_Link">Park SH, Mei C, Pauly M, Garlock R, Dale BE, et al. (2012) Down-regulation of Maize Cinnamoyl-CoA Reductase via RNAi Technology Causes Brown Midrib and Improves AFEXTM-Pretreated Conversion into Fermentable Sugars for Biofuels. Crop Sci 52:2687-2701.


16. value="16" id="Reference_Titile_Link">Fu C, Mielenz JR,Xiao X,Ge Y, Hamilton CY, et al. (2012) Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass. PANS 108: b3803-3808.

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