io butanol Production from Brewery’s Spent Grain Hydrolysate by Clostridium/Eubacterium and Bacillus subtilis
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Date
2018-06
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Addis Ababa University
Abstract
Butanol (butyl alcohol or n-butanol) is a four carbon straight chained alcohol which can be used
as a liquid transportation biofuel. The objective of this study was production of bio butanol from
brewery spent grain (BSG) which in effects to minimize energy cost and substituting nonrenewable
energy by using renewable resources. The chemical and proximate compositions analysis was
investigated. The moisture, ash, extractives, hemicellulose, lignin and cellulose contents were,
64.65, 4.2, 33.28, 17.79 and 17.87 wt. % respectively. The conversion of BSG to bio butanol can
be achieved mainly by four process steps,pre-treatment, hydrolysis (dilute acid hydrolysis),
fermentation and separation. Dilute acid hydrolysis was employed, because it is easy and
productive process. Fermentation of the hydrolyzate was performed using 10 % v/v
Clostridium/Eubacterium at 37
C temperature, pH 6.5 and 96 hr fermentation time for all samples.
The experiment was designed by Box-Behnken Design (BBD) using Design expert 7.0.0 software
with three factors to investigate the effect of (temperature, reaction time and acid concentration).
Hydrolysis temperature was varied from 115°C to 135℃, reaction time was varied from 30 to 40
minutes and the acid concentration was varied from 1.5% to 2%. Significance of the process
variables were analyzed using analysis of variance (ANOVA) and the quadratic model was fitted
to the experimental results. Thus, the influence of all experimental variables, factors and
interaction effects on the response was investigated. Among the investigated components
hydrolysis temperature, reaction time, acid concentration, interaction between temperature and
reaction time, interaction between temperature and acid concentration contributed a significant
effect on the yield of bio butanol. As the result of RSM optimization, the best yield of total reducing
sugar (TRS) and bio butanol were found at 127.42
0
C hydrolysis temperature, 34.32min reaction
time and 1.65% w/w acid concentration. Under these conditions, 59.0 g/L total reducing sugar
(TRS), 10.93 g/L biobutanol yield and 0.11 g/L.h of productivity were obtained. The optimized
process variables were farther enhanced by co culturing Clostridium/Eubacterium and Bacillus
subtilis. Different inoculum concentration ratios (10:1%, 10:3%, and 10:5% v/v) of
Clostridium/Eubacterium to Bacillus subtilis) were used to ferment BSG hydrolysate. The results
exhibited that the inoculum size of 10% Clostridium/Eubacterium with 1% Bacillus subtilis
maximised the production of biobutanol to 13.76g/L and 0.14 g/L.h productivity.
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Keywords
Brewery’s Spent, butanol Production, Bio butanol Production, Grain Hydrolysate, Bacillus subtilis, Clostridium/Eubacterium