Process Improvement of Pharmaceutical Grade Ethanol Production Using Sweet Sorghum

7/26/2019 Process Improvement of Pharmaceutical Grade Ethanol Production Using Sweet Sorghum

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Process Improvement of Pharmaceutical Grade Ethanol Production Using

Sweet Sorghum

1Najiah Nadir, 1Maiirwan Mel, 1Mohd Ismail !"dul #arim, $%osli Mohd &unus

1

Bioprocess Engineering Research GroupDepartment of Biotechnology Engineering,Faculty of Engineering,

International Islamic University Malaysia, P ! Bo" 1#, $#%&' (uala )umpur, Malaysia

&Department of *hemical Engineering

Faculty of *hemical + atural Resources Engineering,

Universiti Malaysia Pahang, ME* *ity, &-.## Gam/ang, (uantan, Pahang, Malaysia

______________________________________________________________________________!"stract

The conversion of starch to sugar can be achieved by hydrolysis process. The two-step enzymatic hydrolysis ofsweet sorghum was performed by commercially available -amylase and glucoamylase and further ethanolfermentation of the obtained hydrolyzates by 0accharomyces cerevisiaewas studied. In order to attain a higherethanol yield, optimization study was carried out in the 2 litres stirred tan bioreactor, !-!raun fermenter toinvestigate the effect of main factors of the hydrolysis process, namely, amount of substrate, temperature, time, andamount of enzyme for the ma"imum production of bioethanol. #s shown in the analysis of variance $#%&'#(result, the amount of substrate, li)uefaction and saccharification temperature have contributed more significanteffect on hydrolysis process of sweet sorghum.

KEYWORDS: sweet sorghum; Saccharomyces cerevisiae; hydrolysis; fermentation; ethanol

1' Introduction

The world

s leading manufacturers andindustries are seeing to substitute petrochemical-based feedstoc with agricultural-based materials aspetroleum supplies continue to decline *+. reatattention has been given to the ethanol productionusing various substrates which can be classified intothree main types of materials, which are sugars $fromsugarcane, sugar beet, sweet sorghum, molasses, andfruits(, starches $from sweet sorghum grain, cassava,corn, potato, and root crops(, and cellulose materials$from agricultural residue, wood, and paper mills(*2, because of the increase in demand for ethanolwhich is considered as an alternative energy source*.

/weet sorghum $0orghum /iocolor $0.( 1oench(is one of the most favourable crops for industrialapplications *+. /orghum is a 3plant characterized

by a high biomass- and sugar-yielding crop *3. Itcontains appro"imately e)ual )uantities of soluble$glucose and sucrose( and insoluble carbohydrates$cellulose and hemicellulose( *4. /weet sorghum hasthe ability of remaining dormant during the driest

periods and is often 5udged to be one of the most

drought resistant agricultural plants *6, 7. Thus, itcan be planted primarily in semiarid and dried parts

of the world, especially in areas too dry for maize *+.#lso, it has been considered as an important energyplant for the production of fuel bioethanol *8.

/weet sorghum grain is a starch-rich grain *+./tarch consists of two types of polysaccharides, thelinear molecule, amylose and a highly branchedmolecule, amylopectin *9. #mylose is a linearmolecule of $+3( lined -:-glucopyranosyl units$-:-$+3(-glucan(, but it is well established thatsome molecules are slightly branched by $+6(--linages. 1eanwhile, amylopectin is a highly

branched component of starch formed through chainsof -:-glucopyranosyl residues lined togethermainly by $+3( linages but with 4-6; of $+6(

bonds at the branch points. It is a branchedpolysaccharide composed of hundreds of short$+3(--glucan chains, which are interlined by$+6(--linages *+


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/tarchy grains and effluent generated from starchprocessing units are the cheap feedstocs and couldbe used as potential raw materials for ethanolfermentation *+2. The sweet sorghum starchhydrolysis may be regarded as a first and importantstep in sorghum processing for bioethanol production*++. =nzymatic hydrolysis is essential for the

production of glucose syrups from starch because ofthe specificity of enzymes allows the sugar syrups

production with well-defined physical and chemicalproperties and the milder enzymatic hydrolysisresults in few side reactions and less browning*2. onventional process for production of

bioethanol from starch basically involved a three-stage process li)uefaction of starch by -amylase,saccharification of li)uefied starch by glucoamylaseand followed by fermentation of sugar to ethanolusing 0accharomyces cerevisiae*++, +2.

The aim of this study was to investigate theli)uefaction and saccharification processes of sweet

sorghum by commercially available -amylase andglucoamylase and ethanol fermentation of theobtained hydrolyzates by 0accharomyces cerevisiaeyeasts. The conditions of starch hydrolysis such asthe substrate and enzyme concentration and thetemperature and time re)uired for the enzymaticaction were optimized taing into account both theeffects of hydrolysis and the ethanol fermentation.Then, the most significant factors that affect thehydrolysis and fermentation processes have been)uantified from the /T#TI/TI# 8 of Taguchi&rthogonal #rray :esign for the ma"imum ethanolyield.

$' Materials and Methods

$'1' Su"strates

/weet sorghum grains were obtained fromIndonesian supplier and blended into small size ofappro"imately +m to enhance the hydrolysis

process.

$'$' Microorganisms

0accharomyces cerevisiaeyeast was obtained from

local maret in dry form. ?or inoculum, +


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Table +.Independent variables in the e"perimental design

'ariables /ymbol oded levels0ow $+( Bigh $2(

#mount of substrate, g # 2

variables. The matching )uality of the data obtainedby the model proposed in =)uation $+( was evaluatedconsidering the correlation coefficient, J2, betweenthe e"perimental and modeled data.


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Table 3.Jegression /ummary

!eta /tandard =rror of !eta

! /tandard=rror of !

t$( p-level

Intercept .42974<


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('(' Effect of l i3uefaction temperature

?ig. . =ffect of li)uefaction temperature on ethanolconcentration

?rom ?ig. +, it can be seen that the li)uefactiontemperature gives positive effect because ethanolconcentration increases as the temperature increases.#s stated by #ggarwal et al*+, li)uefaction under

pressurized steam at +


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('.' Effect of saccharification temperature

?ig. 6. =ffect of saccharification temperature onethanol concentration

?rom ?ig. +, it can be seen that thesaccharification temperature gives negative effectbecause ethanol concentration decreases as thetemperature increases. #s stated by #ggarwal et al*+, the ma"imum saccharification occurred at 34 @

because the rate of saccharification reducedsubstantially at higher temperature. Bowever, theglucoamylase enzyme activity increased

progressively with an increase in temperature from2< @ and reaching ma"imum at 6< @ *+6.1eanwhile, from ?ig. 6, the interaction betweensaccharification temperature and substrateconcentration provides highest effect compared to theinteraction of other factors as the p-value is the

lowest. !ut the interaction was not significant to theethanol production as the p-value is greater than


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*2 F. 0in, /. Tanaa, =thanol fermentationfrom biomass resourcesG current state and

prospects, #pplied 1icrobiology and!iotechnology 69 $2

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Process Improvement of Pharmaceutical Grade Ethanol Production Using Sweet Sorghum