Biomedical Engineering Reference
In-Depth Information
or because of relative brittleness and dryness of sorghum injera after storage
[
60
]. Kisra (aseeda or aceda) is a traditional bread for Arabian Gulf, Sudan, and
Iraq which is similar to injera. It is made from the fermented dough of sorghum
(
Sorghum bicolor
) or pearl millet (
Pennisetum typhodium
) grains. The fermented
dough is baked into thin sheets and consumed along with stew prepared from
vegetables and meat.
Lactobacillus
sp.,
Acetobacter
sp., and
S. cerevisiae
were
the main microflora isolated from kisra and responsible for the fermentation process
[
61
]. Studies on kisra preparation indicated that the fermentation of kisra enhanced
riboflavin and significantly decreased thiamine, without any change in the mineral
contents [
62
]. Sweet sorghum porridges produced by hard grain and cysteine
addition to wheat flour accelerated the stress and structural relaxation [
63
] and
reduced the mixing time by facilitating the breakdown of the wheat proteins by
splitting the disulfide bonds rapidly thus aiding faster dough development
[
64
]. Addition of
L
-cysteine hydrochloride (0.1 %) increased water absorption,
but decreased dough development time and dough stability [
65
]. The Pampanga
Agricultural College, Philippines, has pioneered in this work and published a
compendium that enlisted a huge array of products such as cakes, cookies, biscuits,
rice, porridges and beverages.
Bioethanol
Sorghum-based ethanol production is a very recent area (two decades old) which
involves preprocessing steps like harvest approaches [
66
], juice processing tech-
niques [
67
], as well as fermentation and depends on yeast strain used and yield
ranges from 78 to 90 % [
68
,
69
]. Biomass-based solid-phase fermentation and
juice-based liquid batch fermentation [
70
] and fed-batch fermentation [
71
] were
also been investigated. Application of immobilized yeast in a fluidized bed reactor
[
72
], gelatin bead-packed bed reactor [
73
], stirred tank, and tubular bioreactors [
74
]
as well as application of statistical approaches [
72
] and use of very high gravity
(VHG) [
75
] shortened the fermentation time significantly and increased the con-
version efficiency. Higher ethanol yields were reported by fermenting 30 % sulfuric
acid-treated sorghum [
76
] and from sorghum fibers pretreated with dilute ammonia
followed by enzymatic hydrolysis and fermentation [
77
]. Specifically, the energy
yield from ethanol obtained from the above-referenced studies ranged between
6,500-8,900 kJ/kg dry and 1,400-2,700 kJ/kg fresh sorghum biomass, respectively
(assuming that the energy yield from ethanol is 26,500 kJ/kg). To date, ethanol and
methane are the well-known microbial-derived products from sweet sorghum
[
78
]. The data indicates that from a metric ton of sweet sorghum having 18 %
Brix, 350-450 L of juice can be realized and up on fermentation 45-55 L of
transport grade ethanol can be realized [
2
-
4
]. The utilization of bagasse has a
most promising future for its conversion to ethanol or butanol, while the residual
solids (mainly lignin) can be incinerated to cogenerate heat and power [
2
]. Other
byproducts of sweet sorghum ethanol value chain are vinasse and furnace oil.
Vinasse can be converted into a valuable fertilizer.
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