Physico-chemical and microbiological analyses of fermented corn cob, rice bran and cowpea husk for use in composite rabbit feed.
ABSTRACT An experiment was conducted to evaluate the effect of fermentation on the proximate composition of corn cob, rice bran and cowpea husk for use in composite rabbit feed formulations. The test ingredients were moistened with tap water and allowed to ferment naturally at room temperature. During fermentation, samples of the fermenting materials were extracted at zero, 24 and 48 h for physico-chemical and microbiological analyses using standard procedures. The microorganisms associated with the fermenting materials were identified as Rhizopus oligosporus, Aspergillus oryzae, Aspergillus niger, Rhodotorula, Geotrichum candidum, Candida albicans, and Saccharomyces cerevisiae. Two (R. oligosporus and S. cerevisiae) out of microorganisms present were used as starter cultures to ferment the test ingredients and the fermented products were then analyzed. From the results obtained S. cerevisiae enhanced the protein and fat contents while R. oligosporus was able to degrade the fiber significantly.
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ABSTRACT: The experiment was conducted to evaluate the fermentation effect with Rhizopus oryzae in the composition of whole rice bran, which was used as substratum for the fermentative procedure in tray bioreactors at 30 °C for 120 h. During the fermentation, samples were withdrawn in different times (0, 24, 48, 72, 96, and 120 h) for physico-chemical determination using standard procedures. Reductions in moisture, fat, phytic acid, and reducing sugars content of rice bran were respectively 24.6%, 40%, 50%, and 60%. The fermented bran presented an increase of 30% in ash content, 50% in fibers, and 40% in proteins. The digestible amino acid determination indicated 27.6% increase in the digestibility of produced proteins.El experimento fue llevado a cabo para evaluar el efecto de la fermentación con Rhizopus oryzae en la composición de salvado de arroz, el cual fue usado como sustrato para el proceso de fermentación en biorreactores de bandeja a 30 °C durante 120 horas. Durante la fermentación, se tomaron muestras en diferentes momentos (0, 24, 48, 72, 96 y 120 h) para su determinación físico-química usando métodos estándar. La reducción en contenido de humedad, grasa, ácido fítico y azúcares reductores del salvado de arroz fueron respectivamente 24,6%, 40%, 50% y 60%. El salvado fermentado presentó un incremento en 30% de contenido de cenizas, 50% de fibras y 40% de proteínas. La determinación de aminoácidos digeribles indicó un aumento de 27,6% en la digestibilidad de proteínas producidas.CyTA - Journal of Food 11/2010; 8(3):229-236. · 0.50 Impact Factor
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ABSTRACT: The aim of this study was to evaluate fermented rice bran phospholipids, lipids and fatty acid content in a fermentation solid system with Rhizopus oryzae fungus. For this, aliquots were withdrawn every 24h over 120 h. The content of phospholipids was determined by colorimetric method. Esterified fatty acids were separated by gas chromatography, then identified and quantified. The total lipids from fermented rice bran (FB) decreased from 20.4% to 11.2% in the range between 0 h and 120 h of fermentation while phospholipid contents were increased up to 2.4 mg P g(lipid)(-1). In fermented bran, oleic, palmitic and linoleic acids prevailed, with a decrease in saturated fatty acids (20%) and increase in the unsaturated ones (5%). This study showed that rice bran fermentation with R. oryzae can be applied to the production of phospholipids altering the saturated to unsaturated fatty acid ratio.Bioresource Technology 06/2011; 102(17):8335-8. · 5.04 Impact Factor
Physico-chemical and microbiological analyses of fermented corn
cob, rice bran and cowpea husk for use in composite rabbit feed
Oluseyi O. Oduguwaa, Mojisola O. Edemab,*, Ayodeji O. Ayenia
aDepartment of Animal Nutrition, University of Agriculture, Abeokuta, Nigeria
bDepartment of Microbiology, University of Agriculture, Abeokuta, Nigeria
Received 13 January 2007; received in revised form 21 March 2007; accepted 21 March 2007
Available online 14 May 2007
An experiment was conducted to evaluate the effect of fermentation on the proximate composition of corn cob, rice bran and cowpea
husk for use in composite rabbit feed formulations. The test ingredients were moistened with tap water and allowed to ferment naturally
at room temperature. During fermentation, samples of the fermenting materials were extracted at zero, 24 and 48 h for physico-chemical
and microbiological analyses using standard procedures. The microorganisms associated with the fermenting materials were identified as
Rhizopus oligosporus, Aspergillus oryzae, Aspergillus niger, Rhodotorula, Geotrichum candidum, Candida albicans, and Saccharomyces
cerevisiae. Two (R. oligosporus and S. cerevisiae) out of microorganisms present were used as starter cultures to ferment the test ingre-
dients and the fermented products were then analyzed. From the results obtained S. cerevisiae enhanced the protein and fat contents
while R. oligosporus was able to degrade the fiber significantly.
? 2007 Elsevier Ltd. All rights reserved.
Keywords: Fermentation; Corncob; Rice bran; Cowpea husk; Proximate composition
In Nigeria large quantities of agriculture and agro-
industrial by-products are generated and most of them
are regarded as waste and non-conventional food stuffs
(Adeniyi and Ehiemere, 2003). There have been attempts
to improve the nutritive value of such agricultural residues
by biological means and these attempts have produced var-
ied results (Belewu, 2001). Fermentation has been identified
as one of such attempts.
Fermentation technology has developed in which for
example a considerable amount of unicellular biomass
referred to as microbial or single cell protein, could be
multiplied by using it to ferment a variety of industrial
by-products containing cellulose which are not directly
utilizable by humans but could serve as renewable
raw materials (Maurice, 2001). These materials include
agricultural and forestry residues, industrial by-products/
wastes, food processing wastes and petroleum based
Promises in exploitation of microorganisms for single
cell protein (SCP) production have been reviewed (Harri-
dan and Senez, 1992; Puniya et al., 1995; Anupama,
2000). The production of various chemicals (ethanol, meth-
ane and hydrogen) and single-cell protein utilizing renew-
able resources by fermentation is becoming increasingly
important in view of the global protein problem. The rapid
population growth rate increases the requirement for pro-
tein and better-quality foods in general. As a consequence,
‘‘better-quality foods’’ implies increased quantities of ani-
mal protein. Animal feed production at present is based
on fish waste and plant protein sources, but because of
their relatively high cost it is necessary to seek others.
Hence, this study is aimed at evaluating the effect of fer-
mentation on the proximate composition of corn cob, rice
bran and cowpea husk for potential use as animal feed
0960-8524/$ - see front matter ? 2007 Elsevier Ltd. All rights reserved.
*Corresponding author. Tel.: +234 8037119671.
E-mail address: firstname.lastname@example.org (M.O. Edema).
Available online at www.sciencedirect.com
Bioresource Technology 99 (2008) 1816–1820
2.1. Collection and processing of samples
Corn cob (CC) and cowpea husk (CH) were collected
from open market and were dry-milled using a hammer
mill while rice bran (RB) was collected from rice mill
2.2. Microbiological analysis
The test ingredients were moistened with water in the
ratio17 ml s/10 g of RB, 23 ml s/10 g CH and 15 ml s/10 g
CC. They were then allowed to ferment naturally at room
temperature. Samples (1 g each) were extracted at zero, 24
and 48 h. Ten-fold serial dilutions of the extracts were car-
ried out and 0.1 ml aliquots of dilutions 10?5, 10?6and
10?7were discharged into sterile Petri dishes before molten
Sabouraud Dextrose Agar (SDA) and Potato Dextrose
Agar (PDA) (Oxoid, UK) were added under aseptic condi-
tions as described by Olutiola et al. (1991). The plates were
incubated at 25 ?C for up to 72 h for isolation and enumer-
ation of fungi.
2.3. Isolation and characterization of yeasts and moulds
During incubation, colonies were randomly picked from
the plates used for fungal counts. The isolates were purified
by sub culturing and grouped according to their cultural
features and micro-morphology. Representative yeast iso-
lates were identified to the level of species according to
the procedures of Kreger-van Rij (1984) by pattern of
assimilation of glucose, sucrose, xylose, maltose, galactose
and ethanol (Bacto Yeast Nitrogen Base, Difco, USA);
production of acid from glucose, sucrose, xylose, trehalose,
raffinose and lactose, production of urease; growth at 37 ?C
and formation of pseudomycelium (PDA, Difco) as well as
citrate and nitrate assimilation.
Mould isolates were identified to the level of genus by
their micro-morphological features as well as the color
and nature of their sporulating structures and conidia with
reference to Barnett and Hunter (1972). They were then
sub-cultured and identified to the level of species according
to Onions et al. (1981).
2.4. Fermentation of substrates with selected
Cultures of isolates for inoculum were prepared using
malt extract and Potato Dextrose broths for yeasts and
molds respectively. Five milliliters sterile broth were added
to the cultures growing on agar slants and shaken to make
suspensions. Each suspension was poured into another
5 ml broth medium in another test-tube and incubated at
30 ?C for 48 h. The cultures were then centrifuged at
4000 rpm for 10 min (Labofuge 200, Kendro Laboratory
Products, Germany), washed in sterile distilled water and
re-centrifuged. The washed cells were then used as inocu-
lum in the fermentation of the test materials (Halm et al.,
17 ml s/10 g of RB, 23 ml s/10 g of CH and 15 ml s/10 g
of CC inoculum containing approximately the same con-
centration of cells was used in all cases for the fermentation
of the substrates. Fermentation was carried out in screw-
(28 ± 2 ?C). The fermentation was solid state substrate fer-
mentation in a closed system.
Two out of the isolated microorganisms (Rhizopus oli-
gosporus and Saccharomyces cerevisiae) were used singly
as starter cultures in fermenting the test ingredients. They
were chosen because of some of the demerits of others
which will be mentioned later.
2.5. Physico-chemical analysis of substrates and products
The processed materials were analyzed before and after
fermentation with selected organisms for the following
pH of the samples were determined by the method of
Tansey (1973) with a pH meter (Mettler-Toledo, Essex
M3509 Type 340). Three readings were taken per sample.
The temperatures of the fermenting materials were
taken at 12 h intervals using a Digitron thermometer model
2.5.3. Proximate composition
Proximate compositions of the samples were determined
by the methods of Association of Official and Analytical
Chemists (A.O.A.C., 1990) on dry matter basis. Ash, crude
protein (N · 6.25), fat (ether extract) and fibre were evalu-
ated. All measurements were made in triplicate. Total car-
bohydrate was calculated by difference.
2.6. Statistical analysis of data
The data generated from this study were subjected to
one-way analysis of variance (ANOVA) at 5% level of sig-
nificance using SPSS11.0 for windows. Means were sepa-
rated by Duncan’s multiple range tests.
3. Results and discussion
Table 1 shows the total microbial counts during fermen-
tation. This is the average number of viable cells of micro-
organisms that were present per ml of sample in each plate.
The results show that the numbers of cells increased sig-
nificantly with time. This is expected under favourable con-
ditions and in the presence of nutrients. The increase in
growth rate also shows that the microorganisms were able
to utilize the available nutrients in the test materials.
O.O. Oduguwa et al. / Bioresource Technology 99 (2008) 1816–1820
Table 2 shows the isolated microflora and their distribu-
tion in the substrates fermented. Seven different micro-
organisms were isolated from all the substrates. They were
identified as R. oligosporus, Aspergillus oryzae, Aspergillus
niger, Rhodotorula, Geotrichum candidum, Candida albi-
cans, and S. cerevisiae. A. oryzae and A. niger are known
to be aflatoxin producers, C. albicans is a commensal path-
ogen of humans and its presence could be as a result of
contamination while Rhodotorula is a slow-growing organ-
ism. Therefore, R. oligosporus and S. cerevisiae were
selected for use as test organisms for fermentation of the
The proximate composition and fibre fractions of the
fermented and unfermented crop residues are shown in
Table 3. Significant differences (P 6 0.05) were observed
in the values obtained for fermented and unfermented sam-
ples except in Acid Detergent Fibre (ADF) values for rice
bran. There were no significant differences in ash contents
of samples fermented with R. oligosporus and S. cerevisiae.
There were also no significant differences in crude protein
values obtained for rice bran and cowpea husk fermented
with either of the organisms but the values were signifi-
cantly higher than those obtained for the unfermented sam-
ples. The increase in protein content of the fermented
products may be as a result of microbial cell biomass.
These microbes especially S. cerevisiae are often referred
to as single cell protein because of their high protein con-
tents which has been known to contribute to the protein
contents of various materials (Humphrey et al., 1977; Cha-
hal et al., 1979). This observation is in accordance with the
work of Soccol, 1994 who used R. oligosporus to bio-trans-
form cassava and this led to enhanced protein content.
Charlotte (2002) reported a similar work in which R. oli-
gosporus along with Trichoderma hazarium and A. niger
enhanced the protein content of pulp of sweet potatoes.
The proximate analysis also revealed that cowpea husk
and rice bran had higher crude protein and lower crude
fibre content both in fermented and unfermented products.
The trend of result observed in unfermented crop residues
Total microbial counts (IO4) during fermentation microbial counts
Time (h)024 48
Values are means of three replicates. Mean values followed by different
subscripts along rows are significantly different by Duncan’s multiple
range tests (P 6 0.05).
Distribution of isolated microbes in substrates samples/hours of fermentation
+, present; ?, absent; CC0, corn cob at zero hour; CC24, corn cob at 24th hour; CC48, corn cob at 48th hour; RB0, rice bran at zero hour; RB24, rice bran
at 24th hour; RB48, rice bran at 48th hour; CH0, cowpea husk at zero hour; CH24, cowpea husk at 24th hour; CH48, cowpea husk at 48th hour.
The proximate composition (%) of fermented and unfermented samples
DMCP EECF NDFADFASHNFE
Fermented (with R. oligosporus)
Fermented (with S. cerevisiae)
DM, dry matter; EE, ether extract; NDF, neutral detergent fibre; ASH, ash content; CP, crude protein; CF, crude fibre; ADF, acid detergent fibre; NFE,
nitrogen free extract. Values followed by different subscripts within columns are significantly different by Duncan’s multiple range tests (P 6 0.05).
O.O. Oduguwa et al. / Bioresource Technology 99 (2008) 1816–1820
may be due to presence of high cell content in corn cob and
rice bran (Jess and Michael, 1989) and lower cell wall con-
tent in cowpea husk (Oosting et al., 1993). Fermentation
generally reduced crude fibre content in crop residues espe-
cially when fermented with fungi (Belewu, 2003) because
they possess ability to produce cellulase that degrade
Fiber content is shown to be degraded better by R. oli-
gosporus. This may be connected with its hyphal mode of
growth. The formation of rhizoids could have enhanced
its ability to penetrate the solid substrates and attack the
nutrients therein. In addition, the hydrolytic enzymes
which are secreted at the hyphal tip help the organism in
bio-degradation of complex materials such as those avail-
able in the test substrates used in this study (Maurice,
2001). A combination of these and other factors may
enhance effective fermentation. Various yeast species have
been tested for the production of single cell protein from
a variety of substrates (Ashy and Abou-Zeid, 1982; Jwanny
and Rashad, 1985) neutral detergent fibre (NDF) fraction
were higher but not significant in fermented products espe-
cially R. oligosporus fermented CH. This observation
shows that microbes were able to degrade the fibre fraction
which leads to more soluble fibre fraction (hemicelluloses
and cellulose) in the product. Ash content of the fibre
sources increased slightly. This observation could not be
easily explained, but the presence of silica in RB (Lechlerg
et al., 1987) cannot be ruled out for its high content of ash.
A slightly lower value was obtained for nitrogen free
extract (NFE), the reduction of NFE in fermented prod-
ucts may be linked with the activities of the micro flora
i.e. the utilization of the soluble portion of the carbohy-
drate (which constitute the NFE) by the microbes.
Feed is a relatively high-cost item in the production of
meat, fresh milk, eggs, and broilers. One way to solve this
problem is to develop and implement the use of SCP for
animal feeding. SCP can replace some of the usual protein
sources in feedstuffs; soybean meal, fish meal, or skim-milk
powder will be replaced by SCP with an equivalent amount
of protein. Bioconversion of agricultural and industrial
wastes to protein-rich food and fodder stocks has an addi-
tional benefit of making the final product cheaper. This
would also offset the negative cost value of wastes used
as substrate to yield SCP (Anupama, 2000). Further, it
would make food production less dependent upon land
and relieve the pressure on agriculture.
The results of the study indicate that:
– Protein content of the crop residues was increased signif-
icantly with fermentation while fibre content was signif-
– R. oligosporus was able to degrade the fibre level better
than S. cerevisiae.
The fermented substrates have been used in formula-
tions for rabbit feed by the authors and the results of
the feeding trials are being considered for publication
Use of mixed cultures in the fermentation, use of other
fungi like Trichoderma and some bacteria like Cellulo-
monas, effect of fermentation on vitamin, mineral and
amino acid contents of the test substrates and use of mix-
tures of substrates in fermentation are the focus of ongoing
research by the authors.
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