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3?Conclusions and Future Perspectives

3?Conclusions and Future Perspectives

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8 Molecular Genetic Strategies


cellulosic ethanol is imperative. In order to achieve this, it is important to generate

sufficient amounts of cellulosic biomass. Well over a trillion liters of ethanol

(theoretical yield per year) can be obtained if all the available corn stover, rice

straw and wheat straw (estimated 3 billion tons per year, [6]) are utilized for

biofuel production. This represents one year’s oil demand of USA or approximately 25% of the annual world usage of petroleum. Currently, a significant

amount of straw is either burnt and disposed off or used for animal feed. Therefore,

use of non-food crop biomass plants becomes essential to broaden the availability

of raw material for bioethanol production. Unlike with food crops, objections will

be minimal if genetic modification strategies are applied to the biofuel plants to

enhance yield, be tolerant to stresses and adverse growth conditions.

We have identified manipulation of the intermediates of phytohormone signaling pathways as an important strategy for enhancing plant biomass. The key

developmental processes affecting biomass, which include reduced apical dominance and increased branching, plant height, leaf area and root to shoot ratio etc.,

are strongly influenced by phytohormones. The fact that phytohormones have

pleiotropic effects on growth and development combined with the recent findings

of the multiple signaling intermediates presents tremendous untapped opportunities for modifying specific traits listed above for improvement of the biofuel

plants. The various signaling intermediates and downstream target genes can serve

as candidates for biotechnological improvement or future marker-assisted breeding


The foregoing discussion has highlighted the need for and feasibility of using

genetic and biotechnological approaches to enhance biomass production from a

unit land area. Knowledge gained from model plants can be adapted to the biofuel

crops in order to achieve this and to ensure sustainable biofuel production as a

valuable alternative fuel in the decades to come.

Acknowledgments We thank Ms. Petra Stamm for helping to prepare Fig. 8.1. Research in the

author’s laboratory is funded by the Science and Engineering Research Council (SERC Grant

No.: 0921390036) of the Agency for Science Technology and Research, Singapore; and the

National University of Singapore.


1. Schmer MR, Vogel KP, Mitchell RB, Perrin RK (2008) Net energy of cellulosic ethanol from

switchgrass. Proc Natl Acad Sci USA 105:464–469. doi:10.1073/pnas0704767105

2. Demirbas A (2009) Political, economic and environmental impacts of biofuels: a review.

Appl Energ 86:S108–S117. doi:10.1016/j.apenergy.2009.04.036

3. Milliken J, Joseck F, Wang M, Yuzugullu E (2007) The advanced energy initiative. J Power

Sources 172:121–131. doi:10.1016/j.jpowsour.2007.05.030

4. Heaton EA, Long SP, Dohleman FG (2008) Meeting US biofuel goals with less land: the

potential of Miscanthus. Glob Change Biol 14:2000–2014. doi:10.1111/j.13652486.2008.01662.x


R. Ramamoorthy and P. P. Kumar

5. Kim S, Dale BE (2004) Global potential bioethanol production from wasted crops and crop

residues. Biomass Bioenerg 26:361–375. doi:10.1016/j.biombioe.2003.08.002

6. Binod P, Sindhu R, Singhania RR, Vikram S, Devi L, Nagalakshmi S, Kurien N, Sukumaran

RK, Pandey A (2010) Bioethanol production from rice straw: an overview. Bioresour

Technol 101:4767–4774. doi:10.1016/j.biortech.2009.10.079

7. Engel R, Long D, Carlson G, Wallander R (2005) Estimating straw production of spring and

winter wheat. Fertilizer Facts Montana State University Extention Bulletin No.33

8. Vogel KP, Brejda JJ, Walters DT, Buxton DR (2002) Switchgrass biomass production in the

Midwest USA: harvest and nitrogen management. Agron J 94:413–420

9. McLaughlin SB, Kiniry JR, Taliaferro CM, Ugarte DD (2006) Projecting yield and utilization

potential of switchgrass as an energy crop. Adv Agron 90:267–297. doi:10.1016/S00652113(06)90007-8

10. Parrish DJ, Fike JH (2009) Selecting, establishing, and managing switchgrass (Panicum

virgatum L.) for biofuels. Methods Mol Biol 581:27–40. doi:10.1007/978-1-60761-214-8_2

11. Wang Y, Li J (2008) Molecular basis of plant architecture. Annu Rev Plant Biol 59:253–279.


12. Bennett T, Leyser O (2006) Something on the side: axillary meristems and plant

development. Plant Mol Biol 60:843–854. doi:10.1007/s11103-005-2763-4

13. Lewis JM, Mackintosh CA, Shin S, Gilding E, Kravchenko S, Baldridge G, Zeyen R,

Muehlbauer GJ (2008) Overexpression of the maize Teosinte Branched1 gene in wheat

suppresses tiller development. Plant Cell Rep 27:1217–1225. doi:10.1007/s00299-008-05438

14. Tantikanjana T, Yong JW, Letham DS, Griffith M, Hussain M, Ljung K, Sandberg G,

Sundaresan V (2001) Control of axillary bud initiation and shoot architecture in Arabidopsis

through the SUPERSHOOT gene. Genes Dev 15:1577–1588. doi:10.1101/gad.887301

15. Stirnberg P, van De Sande K, Leyser HM (2002) MAX1 and MAX2 control shoot lateral

branching in Arabidopsis. Development 129:1131–1141

16. Miura K, Ikeda M, Matsubara A, Song X-J, Ito M, Asano K, Matsuoka M, Kitano H, Ashikari

M (2010) OsSPL14 promotes panicle branching and higher grain productivity in rice. Nat

Genet 42:545–549. doi:10.1038/ng.592

17. Zhang HN, Altpeter F, Lomba P (2007) Improved turf quality of transgenic bahiagrass

(Paspalum notatum Flugge) constitutively expressing the ATHB16 gene, a repressor of cell

expansion. Mol Breeding 20:415–423. doi:10.1007/s11032-007-9101-2

18. Takeda T, Suwa Y, Suzuki M, Kitano H, Ueguchi-Tanaka M, Ashikari M, Matsuoka M,

Ueguchi C (2003) The OsTB1 gene negatively regulates lateral branching in rice. Plant J


19. Kebrom TH, Burson BL, Finlayson SA (2006) Phytochrome B represses Teosinte Branched1

expression and induces sorghum axillary bud outgrowth in response to light signals. Plant

Physiol 140:1109–1117. doi:10.1104/pp.105.074856

20. Poethig RS (1990) Phase-change and the regulation of shoot morphogenesis in plants.

Science 250:923–930

21. Kapanigowda M, Stewart BA, Howell TA, Kadasrivenkata H, Baumhardt RL (2010)

Growing maize in clumps as a strategy for marginal climatic conditions. Field Crop Res

118:115–125. doi:10.1016/j.fcr.2010.04.012

22. Aloni R (2001) Foliar and axial aspects of vascular differentiation: hypotheses and evidence.

J Plant Growth Regul 20:22–34

23. Krecek P, Skupa P, Libus J, Naramoto S, Tejos R, Friml J, Zazimalova E (2009) The PINFORMED (PIN) protein family of auxin transporters. Genome Biol 10:249. doi:10.1186/gb2009-10-12-249

24. Ongaro V, Leyser O (2007) Hormonal control of shoot branching. J Exp Bot 59:67–74.


25. Shimizu-Sato S, Tanaka M, Mori H (2008) Auxin–cytokinin interactions in the control of

shoot branching. Plant Mol Biol 69:429–435. doi:10.1007/s11103-008-9416-3

8 Molecular Genetic Strategies


26. Umehara M, Hanada A, Yoshida S, Akiyama K, Arite T, Takeda-Kamiya N, Magome H,

Kamiya Y, Shirasu K, Yoneyama K, Kyozuka J, Yamaguchi S (2008) Inhibition of shoot

branching by new terpenoid plant hormones. Nature 455:195–200. doi:10.1038/nature07272

27. Eriksson ME, Israelsson M, Olsson O, Moritz T (2000) Increased gibberellin biosynthesis in

transgenic trees promotes growth, biomass production and xylem fiber length. Nat Biotechnol


28. Biemelt S (2004) Impact of altered gibberellin metabolism on biomass accumulation, lignin

biosynthesis, and photosynthesis in transgenic tobacco plants. Plant Physiol 135:254–265.


29. Dayan J, Schwarzkopf M, Avni A, Aloni R (2010) Enhancing plant growth and fiber

production by silencing GA2-oxidase. Plant Biotechnol J 8:425–435. doi:10.1111/j.14677652.2009.00480.x

30. Michaels SD, Amasino RM (1999) The gibberellic acid biosynthesis mutant ga1-3 of

Arabidopsis thaliana is responsive to vernalization. Dev Genet 25:194–198. doi:10.1002/


31. Bonetta D, McCourt P (2005) Plant biology: a receptor for gibberellin. Nature 437:627–628.


32. Riefler M, Novak O, Strnad M, Schmulling T (2006) Arabidopsis cytokinin receptor mutants

reveal functions in shoot growth, leaf senescence, seed size, germination, root development,

and cytokinin metabolism. Plant Cell 18:40–54. doi:10.1105/tpc.105.037796

33. Mockaitis K, Estelle M (2008) Auxin receptors and plant development: a new signaling










34. Argueso CT, Raines T, Kieber JJ (2010) Cytokinin signaling and transcriptional networks.

Curr Opin Plant Biol 13:533–539. doi:10.1016/j.pbi.2010.08.006/s1369-5266(10)00108-1

35. Stamm P, Ramamoorthy R, Kumar PP (2011) Feeding the extra billions: strategies to

improve crops and enhance future food security. Plant Biotechnol Rep 5:107–120.


36. Godge MR, Kumar D, Kumar PP (2008) Arabidopsis HOG1 gene and its petunia homolog

PETCBP act as key regulators of yield parameters. Plant Cell Rep 27:1497–1507.


37. Wulfetange K, Lomin SN, Romanov GA, Stolz A, Heyl A, Schmulling T (2011) The

cytokinin receptors of Arabidopsis are located mainly to the endoplasmic reticulum. Plant

Physiol 156:1808–1818. doi:10.1104/pp111.180539

38. Krysan PJ, Young JC, Sussman MR (1999) T-DNA as an insertional mutagen in Arabidopsis.

Plant Cell 11:2283–2290

39. Jeon JS, Lee S, Jung KH, Jun SH, Jeong DH, Lee J, Kim C, Jang S, Yang K, Nam J, An K,

Han MJ, Sung RJ, Choi HS, Yu JH, Choi JH, Cho SY, Cha SS, Kim SI, An G (2000) T-DNA

insertional mutagenesis for functional genomics in rice. Plant J 22:561–570

40. Fedoroff N, Wessler S, Shure M (1983) Isolation of the transposable maize controlling

elements Ac and Ds. Cell 35:235–242. doi:10.1016/0092-8674(83)90226-X

41. Tissier AF, Marillonnet S, Klimyuk V, Patel K, Torres MA, Murphy G, Jones JD (1999)

Multiple independent defective suppressor-mutator transposon insertions in Arabidopsis: a

tool for functional genomics. Plant Cell 11:1841–1852

42. Ramachandran S, Sundaresan V (2001) Transposons as tools for functional genomics. Plant

Physiol Bioch 39:243–252

43. Miftahudin T, Chikmawati K, Ross GJ Scoles, Gustafson JP (2005) Targeting the aluminum

tolerance gene Alt3 region in rye, using rice/rye micro-colinearity. Theor Appl Genet

110:906–913. doi:10.1007/s00122-004-1909-0

44. McCallum CM, Comai L, Greene EA, Henikoff S (2000) Targeting induced local lesions IN

genomes (TILLING) for plant functional genomics. Plant Physiol 123:439–442

45. Tadele Z, Esfeld K, Plaza S (2010) Applications of high-throughput techniques to the

understudied crops of Africa. Aspects Appl Biol 96:223–240


R. Ramamoorthy and P. P. Kumar

46. The International Brachypodium Initiative (2010) Genome sequencing and analysis of the

model grass Brachypodium distachyon. Nature 463:763–768. doi:10.1038/nature08747

47. Martinez-Reyna JM, Vogel KP (2002) Incompatibility systems in switchgrass. Crop Sci


48. Septiningsih EM, Pamplona AM, Sanchez DL, Neeraja CN, Vergara GV, Heuer S, Ismail

AM, Mackill DJ (2009) Development of submergence-tolerant rice cultivars: the Sub1 locus

and beyond. Ann Bot 103:151–160. doi:10.1093/aob/mcn206

49. Somleva MN, Tomaszewski Z, Conger BV (2002) Agrobacterium-mediated genetic

transformation of switchgrass. Crop Sci 42:2080–2087

50. Xi Y, Fu C, Ge Y, Nandakumar R, Hisano H, Bouton J, Wang Z-Y (2009) Agrobacteriummediated transformation of switchgrass and inheritance of the transgenes. BioEnerg Res

2:275–283. doi:10.1007/s12155-009-9049-7

51. Fu C, Mielenz JR, Xiao X, Ge Y, Hamilton CY, Rodriguez M, Chen F, Foston M, Ragauskas

A, Bouton J, Dixon RA, Wang ZY (2011) Genetic manipulation of lignin reduces

recalcitrance and improves ethanol production from switchgrass. Proc Natl Acad Sci USA

108:3803–3808. doi:10.1073/pnas.1100310108

52. Li R, Qu R (2011) High throughput Agrobacterium-mediated switchgrass transformation.

Biomass Bioenerg 35:1046–1054. doi:10.1016/j.biombioe.2010.11.025

53. Zili Y, Zhou P, Chu C, Li X, Li X, Tian W, Wang L, Cao S, Tang Z (2004) Establishment of

genetic transformation system for Miscanthus sacchariflorus and obtaining of its transgenic

plants. High Tech Lett 10:27–31

54. Arencibia AD, Carmona ER, Tellez P, Chan MT, Yu SM, Trujillo LE, Oramas P (1998) An

efficient protocol for sugarcane (Saccharum spp. L.) transformation mediated by

Agrobacterium tumefaciens. Transgenic Res 7:213–222

55. Santosa DA, Hendroko R, Farouk A, Greiner R (2004) A rapid and highly efficient method

for transformation of sugarcane callus. Mol Biotechnol 28:113–119. doi:10.1385/


56. Von Schweinichen C, Buttner M (2005) Expression of a plant cell wall invertase in roots of

Arabidopsis leads to early flowering and an increase in whole plant biomass. Plant Biol

(Stuttg) 7:469–475. doi:10.1055/s-2005-865894

57. Coleman HD, Beamish L, Reid A, Park JY, Mansfield SD (2010) Altered sucrose metabolism

impacts plant biomass production and flower development. Transgenic Res 19:269–283.


58. Wang H, Avci U, Nakashima J, Hahn MG, Chen F, Dixon RA (2010) Mutation of WRKY

transcription factors initiates pith secondary wall formation and increases stem biomass in

dicotyledonous plants. Proc Natl Acad Sci USA 107:22338–22343. doi:10.1073/


59. Salehi H (2005) Delay in flowering and increase in biomass of transgenic tobacco expressing

the floral repressor gene. J Plant Physiol 162:711–717. doi:10.1016/j.jplph.2004.12.002

60. Colasanti J, Yuan Z, Sundaresan V (1998) The indeterminate gene encodes a zinc finger

protein and regulates a leaf-generated signal required for the transition to flowering in maize.

Cell 93:593–603. doi:10.1016/S0092-8674(00)81188-5

61. Cassida KA, Kirkpatrick TL, Robbins RT, Muir JP, Venuto BC, Hussey MA (2005) Plantparasitic nematodes associated with switchgrass (Panicum virgatum L.) grown for biofuel in

the South Central United States. Nematropica 35:1–10

Chapter 9

Production of Bioethanol from Food

Industry Waste: Microbiology,

Biochemistry and Technology

V. K. Joshi, Abhishek Walia and Neerja S. Rana

9.1 Introduction

Ethanol, a solvent, extractant, and antifreeze, is used for synthesis of many solvents in the preparation of dyes, pharmaceuticals, lubricants, adhesives, detergents,

pesticides, explosives, and resins for the manufacture of synthetic fibers and liquid

fuel [163]. Ethanol is a major solvent in industries and ranks second only to water


It is also employed as a solvent for resins, cosmetics and household cleaning

products. The ethanol obtained from biomass-based waste materials or renewable

sources is called as bioethanol and can be used as a fuel, chemical feedstock, and a

solvent in various industries. Besides ethanol, biofuels containing butanol, propanol, 2-methyl 1-butanol, isobutanol, isopropanol, etc. are also employed. Bioethanol produced by fermentation is rapidly gaining popularity all over the world.

The US, Brazil, Japan, France, U.K., Italy, Belgium, and The Netherlands are

among the few countries widely using bioethanol for various uses [98]. It has

certain advantages as petroleum substitutes, viz., alcohol can be produced from a

number of renewable resources, alcohol as fuel burns cleaner than petroleum

which is environmentally more acceptable. It is biodegradable and thus, checks

pollution. It is far less toxic than fossil fuels. It can easily be integrated to the

V. K. Joshi (&)

Department of Food Science and Technology,

Dr. Y.S. Parmar University of Horticulture and Forestry,

Nauni, Solan, Himachal Pradesh, India

e-mail: vkjoshipht@rediffmail.com

A. Walia Á N. S. Rana

Department of Basic Sciences,

Dr. Y.S. Parmar University of Horticulture and Forestry,

Nauni, Solan, Himachal Pradesh, India

e-mail: sunny_0999walia@yahoo.co.in

C. Baskar et al. (eds.), Biomass Conversion,

DOI: 10.1007/978-3-642-28418-2_9, Ó Springer-Verlag Berlin Heidelberg 2012



V. K. Joshi et al.

existing transport fuel system, i.e., up to 5% bioethanol can be blended with

conventional fuel without the need for modification.

Gasohol (mixture of gasoline and alcohol) is widely used to run vehicles in

developed countries. The use of alcohol as fuels is gaining vast popularity day-byday and gasohol program is encouraged throughout the world. By encouraging

bioethanol use, the rural economy could also receive a boost by growing the

necessary crops. New technologies are being developed that are economically and

strategically superior.

The interest in bioethanol as a fuel in response to petroleum price increase is

the most significant factor influencing the world ethanol market. Recent oil

shortage and escalating oil prices have led scientists to develop alternative

energy sources to substitute petroleum. Global warming alerts and threats are on

the rise due to the over utilization of fossil fuels. Alternative fuel sources like

bioethanol and biodiesel are being produced to combat these threats. Bioethanol

production from plant biomass has received considerable attention recently in

order to mitigate global warming and demands for petroleum not from a finite

resource and is a greenhouse gas emission. The road transport network accounts for

22% of all greenhouse gas emissions, and through the use of bioethanol as some of

these emissions will be reduced as the fuel crops absorb CO2. Also, blending

bioethanol with petrol will help extend the life of diminishing oil supplies and

ensure greater fuel security, avoiding heavy dependence on oil producing nations.

Biofuel obtained from renewable sources can be classified on the basis of their

production techniques as given below:

• First-generation fuels refer to biofuels made from plants rich in oil and sugar.

• Second-generation biofuels (Biomass to liquid) are made from organic materials, such as straw, wood residues, agricultural residues, reclaimed wood, sawdust, and low value timber.

• Biofuels of third generation are produced from algae by using modern gene and


• Fourth-generation biofuels are produced from vegetable oil by using hydrolytic


Tables 9.1 and 9.2 show biofuels of the four generations, their substrates and

technological processes of their production.

It is apparent that different types of substrates can be employed to produce

bioethanol. Accordingly, modification in its production technology has been made.

The replacement of ethanol by ethylene is reversed in less industrialized nations.

In Brazil and India, ethylene and its chemical derivates are produced by catalytic

dehydration of fermentative ethanol [5].

The USA and Brazil are currently the primary producers of fuel ethanol, producing 49.6 and 38.3% of the 2007 global production, respectively. US bioethanol

production is almost entirely from maize (corn) starch, which is converted into

fermentable glucose by the addition of amylase and glucoamylase enzymes. In

2007, 24.6 billion L of ethanol was produced in the USA, that comprised of only

3.2% of gasoline consumption on an energy-equivalent basis [188].

9 Production of Bioethanol from Food Industry Waste


Table 9.1 First- and second-generation biofuels, their feedstock, and technological processes of

their production

Type of biofuel


Biomass feedstock



First-generation (conventional) biofuel


Conventional bioethanol

Pure plant oil

Biodiesel fuel (plant


Biodiesel fuel


Sugar beet, sugarcane,

sugar, sorghum

Pure plant oil (PPO)

Oil plants (e.g.


Rape methyl-/ethyl ester

Oil plants (e.g. rape/

(RME/REE) Fatty acids

turnip rape seed,

Methyl/ethyl ester

sunflower seeds,


soy beans, etc.

Fatty acids (waste

Biodiesel cooking and


deep fry grease

ester (FAME/FAEE)

Upgrade biogas

(Wet) biomass



Second-generation Biofuel


Cellulose ethanol


Synthetic biofuels

Mixed higher alcohols Bio- Lignocelluloses

dimethyl ether

Biodiesel (hybrid


Plant oils and animal

biodiesel from the


first and second



SNG(synthetic natural gas) Lignocelluloses



Hydrolysis and













hydrolysis and


Gasification and





Gasification and


Gasification and

syntheses or



Source [172]

Table 9.2 Third- and fourth-generation biofuels, their feedstock, and technological processes

Type of biofuel Name

Biomass feedstock

Production process

Third-generation biofuels


Oligae Algae diesel

Fourth-generation biofuels

Bio gasoline

Synthetic oil

Bio jet fuel


Source [37]


Gene and nanotechnology

and esterification

Vegetable oil (CENTIATM

oil from algae)

Hydrolytic conversion/



V. K. Joshi et al.

Table 9.3 Production cost of various chemicals using ethanol as feedstock


Production cost ($/l)


Acetic acid



2-Ethyl alcohol

From petroleum feedsock

From ethanol (at 40 g/l)











Source [139]

The production costs of various chemicals from ethanol and petroleum feedstocks are compared in Table 9.3. Clearly, the production of bioethanol from first

generation is economically unreasonable because of discarding cellulose and

hemicellulose which constitute the majority of carbon resources of plants. Furthermore, the biofuels of this generation also compete with food products intended

for human consumption. Thus, second-generation bioethanol production is

important as it allows improved CO2 balance and make use of cheap, waste source

which does not compete with human food products.

In brief, the use of ethanol as a biofuel is gaining increasing popularity.

Although it is produced from several sources but the technologies using the waste

material for its production is most attractive as it does not interfere with food

particular substrates needed for the ever increasing world population. Different

types of waste materials, their composition, biochemistry, microbiology, and the

technology involved in bioethanol production have been reviewed in this chapter.

New strategies and future thrust has also been briefly highlighted.

9.2 Raw Materials

9.2.1 Wheat Straw

Wheat (Triticum aestivum L.) is the world’s most widely grown crop, cultivated in

over 115 countries under a wide range of environmental conditions. Over the past

100 years, the yields of wheat have been increased and the annual global production of dry wheat in 2008 was estimated to be over 650 Tg [10]. Assuming

residue/crop ratio of 1.3, about 850 Tg of wheat residues are annually produced

which include straw as the major waste. The straw produced is left on the field,

plowed back into the soil, burnt, or even removed from the land depending on the

convenience of the landowner. Disposal of wheat straw by burning is viewed as a

serious problem due to the increased concern over the health hazards of smoke

generated [93]. Burning of wheat straw also results in production of large amounts

of air pollutants including particulate matter, CO, and NO2 [110]. Thus, finding an

9 Production of Bioethanol from Food Industry Waste


Table 9.4 Composition of arable crop residues based on dry mass (DM) and potential for

bioethanol production


Residue/ DM Cellulose Hemicellulose Lignin Carbohydrates Ethanol

crop ratio (%) (%)




(l/kg DM)





Rice straw








81.0 –

78.5 45







































Source [95, 140, 144]


kg of bagasse/kg of dry sugarcane

alternative way for disposal of surplus wheat straw is of paramount interest and an

immediate necessity.

Wheat straw like any other biomass of lignocellulosic nature is a complex

mixture of cellulose, hemicellulose, and lignin as three main components

(Table 9.4), and a small amount of soluble substrates (also known as extractives)

and ash. The overall chemical composition of wheat straws could slightly differ

depending on the wheat species, soil, and climate conditions. The cellulose strands

are bundled together and tightly packed in such a way that neither water nor

enzyme can penetrate through the structure [104, 179]. Hemicellulose serves as a

connection between lignin and cellulose fibers, and it is readily hydrolyzed by

dilute acid or base, as well as hemicellulase enzyme. Lignin is covalently linked to

cellulose and xylan (predominant hemicellulose carbohydrate polymer in wheat

straw) such that lignin–cellulose–xylan interactions exert a great influence on the

digestibility of lignocellulosic materials [104]. Due to this structural complexity of

the lignocellulosic matrix, ethanol production from wheat straw requires at least

four major unit operations including pretreatment, hydrolysis, fermentation, and

distillation. Unlike sucrose or starch, lignocellulosic biomass such as wheat straw

need to be pretreated to make cellulose accessible for efficient enzymatic


9.2.2 Sugarcane Bagasse

Sugarcane bagasse is the wastes from the sugar factory. It is obtained as a left-over

material after the juice is extracted from the sugarcane. Sugarcane bagasse (SCB)

was analyzed for its composition, structure, and surface properties (Table 9.4).


V. K. Joshi et al.

Because of its lower ash content, 1.9% [111], bagasse offers numerous advantages

compared to other agro-based residues such as paddy straw, 16% [4], rice straw,

14.5% [60], and wheat straw, 9.2% [210]. In another study, SCB was obtained

from a small sugarcane juice factory and milled for analysis of different types of

fibers. It is important to note that most developments in SCB transformation into

sugars and ethanol have a common scientific base with other lignocellulosic

materials, due to considerable similarity in composition and structure.

9.2.3 Rice Straw

Rice straw, a waste from paddy processing, has several characteristics that make it

a potential feedstock for fuel ethanol production. It has high cellulose and hemicellulose content that can be readily hydrolyzed into fermentable sugars. The

chemical composition of feedstock has a major influence on the efficiency of

bioenergy generation. The low feedstock quality of rice straw is primarily determined by a high ash content (10–17%) compared to wheat straw (around 3%) and

also high silica content in ash (SiO2 is 75% in rice and 55% in wheat) [205]. On

the other hand, rice straw as feedstock has the advantage of having a relatively low

total alkali content (Na2O and K2O typically comprise\15% of total ash), whereas

wheat straw can typically have [25% alkali content in ash [12].

In terms of chemical composition, the straw predominantly contains cellulose

(32–47%), hemicellulose (19–27%), and lignin (5–24%) [48, 116, 159, 204] as

shown in Table 9.4. The pentoses are dominant in hemicellulose, in which xylose

is the most important sugar (14.8–20.2%) [149].

9.2.4 Fruit and Vegetable Waste Apple Pomace

Apple pomace is the solid phase resulting from pressing apples for juice, containing the pulp, peels, and cores. It accounts for 25–35% of the dry weight of

processed apple. It has very high moisture content and can be easily decomposed

by microorganisms. It is of yellow-to-brown color [7]. It is a rich source of many

nutrients including carbohydrates, minerals, fibers except protein [162]. Apple

pomace has high contents of carbohydrates with about 9.5–22.0% of fermentable

sugar [174] which makes it a good substrate for fermentation while its low protein

content indicates its unsuitability as animal feed [67, 86].

The amount of initial sugar content, however, depends upon the variety of apple

processed, the processing conditions used, and the amount of filter aids added [66].

9 Production of Bioethanol from Food Industry Waste


Table 9.5 Proximate composition of apple pomace



Moisture (%)

Acidity (% malic acid)

Total soluble solids

(TSS oB)

Total carbohydrate (%)

Glucose (%)

Fructose (%)

Sucrose (%)

Xylose (%)


Vitamin-C (mg/100 g)

Soluble proteins (%)

Protein (%)

Crude fiber (%)

Fat (ether extract, %)

Pectin (%)

Ash (%)

Polyphenols (%)

Amino acids (%)


Potassium (%)

Calcium (%)

Sodium (%)

Magnesium (%)

Copper (mg/l)

Zinc (mg/l)

Manganese (mg/l)

Iron (mg/l)

Calorific value (kcal/100 g)

Wet weight basis

Dry weight basis






















































Source [65, 84, 86, 92, 174]

Alcohol-soluble compounds (monosaccharides, oligosaccharides, and malic acid)

accounted for 32–45 wt% of oven-dry pomace. Glucose and fructose are the major

components of this fraction. Apple pomace is an acidic substrate and has considerable buffering capacity due to the presence of malic acid in it. Apple pomace

has high levels of Biochemical Oxygen Demand/Chemical Oxygen Demand

(BOD/COD) and is highly biodegradable. The proximate composition of apple

pomace is shown in Table 9.5.

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3?Conclusions and Future Perspectives

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