Hibridi kukuruza kao sirovina za proizvodnju bioetanola

Transcription

1 Maize as raw matherial ORIGINAL for SCIENTIFIC bioetanol PAPER Maize as raw matherial for bioetanol Snežana MLADENOVIĆ DRINIĆ 1, Valentina SEMEČENKO 1, Milica RADOSAVLJEVIĆ 1, Dušanka TERZIĆ 1, Milena SIMIĆ 1, Milan STEVANOVIĆ 1, Bojan STIPEŠEVIĆ 2 1 Maize Research Institute, S. Bajića 1, Belgrade, Serbia, ( msnezana@mrizp.rs) 2 Faculty of Agriculture, Trg Sv. Trojstva 3, Osijek, Croatia Abstract Maize is one of the most important naturally renewable sources of carbohydrate raw materials, energy and series of diverse products. Maize can provide both starch (seed) and cellulosic (stover) material for bioethanol production. The aim of this paper is study of the utility of ZP maize hybrids as raw material for bioethanol production. Obtained results show that maize hybrids differ in ethanol yield production. The highest ethanol yield, expressed in% of the theoretical yield, after 34 hours of fermetation was obtained with ZP 434, 90.2% and the lowest one with ZP544, 69.32%. The highest starch-producing hybrid was not the highest ethanol producer. The starch yield and starch recovery are more important traits for ethanol production than starch content. The correlation between these two traits with ethanol yield was 0.37 and 0.57 respectively. The cellulose and hemicelluloses content vary between ZP hybrids from to 21.68% and to 22.92%, respectively. Study of lignocelluloses of ZP maize hybrids as raw material for ethanol production is in progress. Key words: bioethanol, lignocellulose, maize hybrids, starch Hibridi kukuruza kao sirovina za proizvodnju bioetanola Sažetak Cilj rada je ispitati mogućnost korištenja ZP hibrida kukuruza za proizvodnju etanola. Kukuruz daje škrob (zrno) i celulozu (stabljika) kao sirovinu za proizvodnju bioetanola. Dobiveni rezultati pokazali su da je najveći prinos etanola, izražen u% u odnosu na teoretski prinos, imao hibrid ZP 434 (90,2%), a najniži hibrid ZP 544 (69,32%). Hibrid s najvećim sadržajem škroba nije dao najviše etanola. Prinos i obnovljivost škroba su važnija svojstva za proizvodnju etanola od sadržaja škroba. Koeficijenti korelacije između ova dva svojstva s prinosom etanola bili su 0,37 odnosno 0,57. Hibridi kukuruza su se razlikovali po sadržaju celuloze i hemiceluloze. Sadržaj celuloze je bio od 19,17 do 21,68% a hemiceluloze od 19,13 do 22,92%. Korištenje lignoceluloze ZP hibrida kukuruza kao sirovine za proizvodnju bioetanola je u fazi istraživanja. Ključne riječi: bioetanol, hibridi, kukuruz, lignoceluloza, škrob Proceedings. 46 th Croatian and 6 th International Symposium on Agriculture. Opatija. Croatia ( ) Section 5. Field Crop Production 635

2 Snežana MLADENOVIĆ DRINIĆ, Valentina SEMEČENKO, Milica RADOSAVLJEVIĆ, Dušanka TERZIĆ, Milena SIMIĆ, Milan STEVANOVIĆ, Bojan STIPEŠEVIĆ Introduction It has become clear that fossil energy sources of the Earth are finite, moreover, their use causes more and more damages to the environment (climate change, air pollution, greenhouse effect, etc.). Bioethanol is the most commonly used biofuel to substitute for gasoline. It can be combined with gasoline in any concentration up to pure ethanol. It is a renewable, environmentally friendly fuel that is inherently cleaner than gasoline. Using ethanol reduces emissions of carbon monoxide by 32.5%, particulate matter, oxides of nitrogen, and other ozone-forming pollutants and greenhouse gas emissions by as much as percent (Badger, 2002, Demirbas, 2005, Purwadi, 2006). According to Renewable Fuels Association (RFA) in 2009 ethanol fuel production worldwide reached 73.9 milion liters. The world and European production of bioethanol for fuel is constantly increasing, tending to 100 mil L till 2012 (Radosavljević et al, 2009). The consumption of bioethanol in Europe is largest in Germany, Sweden, France and Spain. Europe produces equivalent to 90% of its consumption (Wikipedia, 2010). The two most widely used crops for ethanol production are sugarcane and maize. The production process consists of conversion of biomass to fermentable sugars, fermentation of sugars to ethanol, and the separation and purification of the ethanol. Maize is one of the most important crops, and as such, one of the most significant naturally renewable carbohydrate raw materials of energy and numerous very different products. According to FAO data in 2009 maize was grown on the area of hectares ( The world maize production amounted to 817 million tonnes of grain. The average global yield per hectare has approached the level of five tonnes of grain, while the most developed agricultures have reached the levels of 7-8 tonnes per hectare. The Republic of Serbia is one of more important maize producers not only in Europe but in the world, too. According to FAO data in 2009, maize was grown on areas of approximately ha. The total annual production amounted to t, with an average grain yield of tons per hectare. The interest in producing ethanol from maize has increased during recent years. There are two ways, i.e. procedures of getting ethanol from maize, wet and dry milling. A 25.3 kg of maize grain can produce from 9.4 to 10.9 L of pure ethanol, depending on the technology used. Currently, ethanol is primarily fermented from the sugar that makes up the starch in grain. But ethanol also can be made from celluloses biomass - plant matter composed primarily of inedible cellulose fibers that form the stems and branches of most plants. Lignocellulosic materials, as excellent energy sources, consist primarily of three components, namely cellulose, hemicelluloses and lignin (Ehara and Saka, 2002). The compositions of these constituents may vary from one plant species to another. The composition within a single plant varies with age, stage of growth and other conditions (Purwadi, 2006). Four biologically mediated steps occur in the course of converting lignocelluloses materials into bio-ethanol: (i) cellulose production, (ii) hydrolysis of the cellulose and other insoluble polysaccharides, (iii) fermentation of soluble cellulose hydrolysates and (iv) fermentation of soluble hemicelluloses hydrolysates. A pretreatment step using steam or dilute sulfuric acid is generally used to separate the biomass into its constituent parts - cellulose, hemicelluloses, and lignin. The cellulose and hemicelluloses are then hydrolyzed to sugars - both five-carbon sugars - xylose and arabinose - and sixcarbon sugars - glucose, mannose and galactose. These sugars require specialized microbes or modified yeasts for fermentation. There are three basic types of ethanol-from-cellulose processes acid hydrolysis, enzymatic hydrolysis, and thermochemical with variations for each. The most common is acid hydrolysis. Virtually any acid can be used; however, sulfuric acid is most commonly used since it is usually the least expensive (Badger, 2002). The aim of our study was to analyse the fermentable properties of grain as well as suitability of selected ZP maize hybrids for the bioethanol production. Material and methods Grain of five ZP maize hybrids (ZP-341, ZP-434, ZP-505, ZP-544, ZP-704wx) was milled to flour on the Perten Instruments laboratory mill. Grain starch content was analysed by Ewers polarimetric method (ISO, 1997). Starch yield and recovery was determined by Eckhoff et al., Before ethanol fermentation twostep enzymatic hydrolysis of corn meal by commercially available α-amylase (from Bacillus licheniformis, Termamyl SC, Novozymes, Denmark) and glucoamylase (SAN Extra L, Novozymes, Denmark, from Aspergillus niger) was done (Nikolić et al., 2009). The maize meal hydrolyzates were good substrates for ethanol fermentation by Saccharomyces cerevisiae (collection of BIB-TMF, Belgrade) yeast. The ethanol concentration was determined based on the density of alcohol distillate at 20 ºC and expressed in th Croatian and 6 th International Symposium on Agriculture

3 Maize as raw matherial for bioetanol weight%(w/w), (Official Methods, 2000). Analysis of the content of lignocellulose was performed by the modified Van Soest method (1963). Results and discussion Maize is the most important crop and starch is the most abundant component of the maize kernels. Starch content differs between analysed hybrids. The lowest strach content has hybrid ZP341 (69%) and the higest hybrid ZP704wx, 74.13%, (Table 1). Starch yield is the most important fraction from the wet-milling process (Singh and Eckhoff, 1996) as indicator of millability, or ease with which kernel components are separated by wet milling. In analysed maize hybrids starch yield varied from (ZP704wx) to (ZP434). Starch recovery as an indicator of the starch extractability of a particular hybrid varied from to 93.14%. Starch recoveries were highly correlated with starch yield values (r = 0.82). Table 1. Starch properties of maize hybrids and ethanol content and yield Hybrids Starch content % Starch yield Starch recovery Ethanol content % Etanol yield % ZP a b ns d ZP a c ns e ZP a a ns b ZP a b ns a ZP704wx ab a ns c LSD 5% a-e column means with common superscripts do not differ (p>0.05) Today, ethanol from maize is produced almost exclusively from starch. Starchy materials require a reaction of starch with water (hydrolysis) to break down the starch into fermentable sugars (saccharification). After the two-step enzymatic hydrolysis of five ZP maize hybrids obtained hydrolyzates was subjected to anaerobic fermentation by yeast Saccharomyces cerevisiae to produce ethanol. Ethanol content during the fermentation were determined in samples taken before fermentation and after 24 and 34 hour (Drinic et al., 2010). The highest ethanol content, after 34 hours of fermentation, was obtained from hybrid ZP434, 8.95%, and the lowest from hybrid ZP544, Maize hybrids differ in ethanol yield production. The higest ethanol yield (in% of the theoretical yield) achieved after 34 hours of the fermentation, was obtained with ZP 434, 90, 2% (table 1). The lowest ethanol yield of 69.32% was obtained with ZP 544. The similar ethanol yield (approximately 79%) was also detected in the hybrids ZP 704wx and ZP 341. These two hybrids significantly differ in starch content. If compared ethanol yield of ZP 434 with ethanol yield of some another comercial hybrids, ranged from to 92.35% (Radosavljević et al., 2001; Nikolić et al., 2009), it can be concluded that ZP434 is very suitable for bioethanol production. The relationship between grain starch and ethanol yield is not completely understood. The highest starch-producing hybrid was not the highest ethanol producer (Dein et al., 2002). Our results indicate that starch yield and starch recovery are more important traits for ethanol production than starch content. Coefficient of correlation between strach yield and ethanol yield and ethanol content was 0.37 and 0.22, respectively. Coefficient of correlation between starch recovery and ethanol content and ethanol yield was 0.30 and 0.57, respectively. While ethanol is typically produced from the starch contained in grains, it can also be produced from cellulose. Cellulose is the main component of plant cell walls and is the most common organic compound on earth. Maize stover contains principally cellulose and hemicelluloses which are the main source of fermentable sugars for ethanol production. Lignocelluloses content of ZP hybrids plant was analyzed and results are presented in Table 2. Table 2. Lignocelluloses content of ZP maize hybrids Hybrids Cellulose % Hemicelluloses % ZP a a ZP b b ZP d d ZP e d ZP704wx c c LSD 5% a-e column means with common superscripts do not differ (p>0.05) Section 5. Field Crop Production 637

4 Snežana MLADENOVIĆ DRINIĆ, Valentina SEMEČENKO, Milica RADOSAVLJEVIĆ, Dušanka TERZIĆ, Milena SIMIĆ, Milan STEVANOVIĆ, Bojan STIPEŠEVIĆ The conversion of lignocellulosic material to ethanol is generally more complex, compared to starch hydrolysis and fermentation. Cellulose is difficult to convert into fermentable sugars due to its crystalline structure and closed association with lignin and hemicelluloses. Study of lignocelluloses from ZP maize hybrids as raw material for ethanol production is in progress. If sustainable, cost effective, and enviromentaly compatible agricultural practices are developed and coupled to cellulose conversion tehnology, maize has potential to provide billon galons of ethanol per year through a combination of starch processing and cellulose conversion (Schwietzke et al, 2009). Conclusion The hybrid ZP 434 is extremely suitable for the production of bioethanol and starch, as it had the highest ethanol yield of 90.2% of the theoretical yield, as well as, the maximum yield (65.15%) and starch recovery (93.14%). The starch yield and starch recovery, as indicators of millability and starch extractability, are more important traits for ethanol production than starch content. How in Serbia is enough maize for other purposes besides the food significant amounts can be used for the bioethanol production. Acknowledgement The results presented in the paper are an output from research projects TR Ministry of Science and Technological Development. Serbia and Bilateral project Sustainability of summer second crops for bioenergy needs with R.Croatia. References Badger, P.C. (2002). Ethanol from cellulose: A general review. p In: J. Janick and A. Whipkey (eds.), Trends in new crops and new uses. ASHS Press, Alexandria, VA. Dein, B.S., Bothast R.J., Iten L.B., Barrios L., Eckhoff S.R. (2002). Fate of Bt protein and influence of corn hybrid on ethanol production. Cereal Chem. 79: Demirbas, A (2005). Bioethanol from cellulosic material: A renewable motor fuel from ethanol. Energy sources. 27: Drinić Mladenović Snežana, Radosavljević Milica, Semenčenko Valentina, Milašinović Marija, Filipović Milomir, Dumanović Zoran (2010): "Maize hybrids as raw material for bioethanol production". 3 rd International Scientific/Professional Conference "Agriculture in Nature and Environmental Protection", Proceedings and Abstracts, pp May 31 st - June 2 nd, Vukovar, Croatia Ehara K, Saka S (2002). A comparative study on chemical conversion of cellulose between the batch-type and flow-type systems in supercritical water.cellulose 9, Eckhoff S..R., Singh S.K., Zehr B., Rausch K., Fox E., Mistry A., Haken A., Niu Y., Zou S., Buriak P., Tumbleson M., Keeling P. (1996). A 100g laboratory corn wet-milling procedure. Cereal Chem.73, FAO (2010). International Organization for Standardization (1997).Native starch-determination of starch content -Ewers polarimetric method, IS :1997 Official Methods In: Official Methods of Analysis of AOAC International, 17th ed., Gaithersburg, MD, USA:AOAC International; Nikolić, S, Mojović, L, Rakin, M, Pejin, D., (2009). Bioethanol production from corn meal by simultaneous enzymatic saccharification and fermentation with immobilized cells of Saccharomyces cerevisiae var. ellipsoideus, Fuel, vol88, no.9, Purwadi R. (2006). Continuous ethanol production from dilute-acid hydrolyzates: detoxification and fermentation strategy. PhD Thesis: Department of Chemical and Biological Engineering, Chalmers University of Technology, Gotebery, Sweden. Radosavljević M., Božović I., Bekrić V, Jovanović R, Žilić S., Terzić D. (2001). Savremene metode određivanja kvaliteta i tehnološke vrednosti kukuruza. PTEP- časopis za procesnu tehniku i energetiku u poljoprivredi, 5, th Croatian and 6 th International Symposium on Agriculture

5 Maize as raw matherial for bioetanol Radosavljević, M, Mojović, L, Rakin, M, Milašinović M. (2009). ZP hibridi kukuruz kao sirovina za proizvodnju bioetanola. Journal on processing and Energy in Agriculture (former PTEP), 13 (1), Renewable fuels association, RFA(2009). Annual world ethanol production by country. Singh, N., and Eckhoff, S. R. (1996). Wet milling of corn-a review of laboratory-scale and pilot plant-scale procedures. Cereal Chem.73: Schwietzke S., Kim Y., Ximens E., Mosier N., Ladisch M. (2009). Ethanol production from maize. Chapter 23, pp in Molecular gnetic approaches to maize improvment. A.L.Kriz, B.A.Larkins (eds.), Springer-Verlag Berlin Heidelberg. Van Soest P.J. (1963): use of detergents in the analysis of fibrous feeds. ii. a rapid method for determination of fibre and lignin. J. Assoc. Offic. Anal. Chem.,46, 829. Wikipedia (2010). Ethanol fuel. - cite_note-eubia- 80 sa2011_0511 Section 5. Field Crop Production 639