Proximate composition and amino acid profile of differently fermented cassava tuber wastes collected from a cassava starch producing factory in Nigeria

S O Aro and V A Aletor

Department of Animal Production and Health, Federal University of Technology,
Akure, Nigeria.
sambolaro@yahoo.co.uk

Abstract

Cassava is grown mainly for its tuberous roots whose high carbohydrate content is a cheap source of food that has continued to support the sustenance of millions of people in sub-Saharan Africa, Central America and south-east Asia. The utilization of cassava roots for human consumption and in the industries has led to the generation of different types of wastes aptly called the cassava tuber wastes (CTW). Two of such wastes: the cassava starch residues (CSR) and the cassava peels (CAP) were collected from a cassava starch producing factory, subjected to various forms of solid substrate fermentation with a consortium of micro-organisms and analyzed for their proximate and amino acid composition.

The crude protein content of the CSR increased significantly from 1.12g/100g in the unfermented cassava starch residues (UFCSR) to 7.02g/100g in the microbially fermented cassava starch residues (MFCSR). The CAP protein increased from an initial 5.30g/100g in the unfermented cassava peels (UFCP) to 10.94g/100g in the microbially fermented cassava peels (MFCP). Similar improvement was also observed in the degradation of the crude fibre component of the wastes whose value was decreased from 19.20g/100g to12.06g/100g in UFCSR and MFCSR and from38.44g/100g to 5.88g/100g in UFCP and MFCP respectively. The low energy values of the unfermented wastes were significantly enhanced though fermentation with an increase from 10.74MJ ME/kg (UFCSR) to 12.96MJ ME/kg (NFCSR) and to 13.26MJ ME/kg (MFCSR) in the three CSR samples and from 9.03MJ ME/kg (UFCP) to 13.24MJ ME/kg (NFCP) and to 14.04MJ ME/kg (MFCP) in the CAP samples.  The amino acid profile of these wastes revealed that fermentation led to a significant improvement of the protein quality of the wastes and more so in the naturally fermented cassava starch residues. It could be concluded that fermentation either naturally or with selected micro-organisms has the potentials of enhancing the nutritive value of cassava tuber wastes thus opening a vista of opportunities by which these wastes could be converted to wealth. The livestock industry as the major stakeholder could therefore benefit by way of reduced cost of animal feeds while the environment would also be relieved of the huge volume of wastes being discharged into it.

Keywords: Agro-industry, by-products, livestock, microbes, solid state fermentation

Introduction

Huge quantity of cassava wastes are daily discharged to the environment with unwholesome consequences (Tewe 1996; Aro et al 2010). The effective utilization of these agricultural by-products as a major focus of research especially in developing countries has been canvassed by several authors (Gow-Chin et al 1998; Sucharita et al 1998). There are limitations however to the use of these non-conventional feedstuffs as occasioned by their low protein and high fibre (the non-starch polysaccharides) content coupled with high levels of anti-nutrients (Iyayi et al 1997).

Another constraint to the use of these agro-industrial wastes is the dearth of affordable and sustainable local technologies to modify these products to forms acceptable to our livestock industries. A way out of these problems preventing the full utilization of the agro-industrial “wastes” needs to be sought. The biotechnological option of fermentation, using the generally recognized as safe (GRAS) organisms as the most cost effective solution to these problems has been suggested by several authors (Israelides et al 1998; Oboh and Akindahunsi 2003; Nwafor and Ejukonemu 2004; Aro 2010). The objective of this study therefore was to investigate the effects of fermentation by selected micro-organisms on some cassava tuber wastes in terms of nutrients’ enhancement, biodegradation of crude fibre component  and the amino acid profile of the fermented cassava tuber wastes. This would be done as a prelude to producing value-added modified agro-by-products that are well attuned to sustainable local technologies and the utilization of such value-added products for livestock nutrition. 

Materials Methods

Preparation of cassava tuber waste samples

Fresh cassava tuber wastes (i.e. cassava starch residues [CSR] and cassava peels [CAP]) were collected from Matna Foods Limited in Ogbese, Ondo State, Nigeria. Part of these cassava tuber wastes (CTW) were sun-dried for five days and were thereafter packed in cellophane bags and designated unfermented CTW i.e. unfermented cassava starch residues (UFCSR) [,Photo 1] and unfermented cassava peels (UFCP) [,Photo 2]. Another part of the fresh CTW was kept in two polythene sacks, tied securely, laid on a wooden pallet and left to ferment under a covered shed for five days and thereafter sun-dried and stored under similar environmental condition as in the unfermented samples. These two fermented samples were designated naturally fermented cassava starch residues (NFCSR) and naturally fermented cassava peels (NFCP) respectively. The third part the fresh CTW was sundried and packed in two air-tight nylon bags to await heat sterilization and inoculation with candidate micro-organisms: the fungus-Aspergillus fumigatus and two different strains of lactic acid bacteria (Lactobacillus delbrueckii and Lactobacillus coryneformis). These micro-organisms were isolated and cultured in the Microbiology Laboratory of the Department of Microbiology, Federal University of Technology, Akure, Nigeria.

Photo 1: Sample of unfermented cassava starch residues	Photo 2: Sample of unfermented cassava peels

Two kilogramme (2000g) each of the sun-dried CTW in the two nylon bags meant for microbial inoculation  were weighed into two nylon sachets each containing a sample of CSR and CAP respectively. 2500mls of sterile water were added to the CSR sample while 2000mls were added to the CAP sample. The difference in the quantity of water added is as a result of differences in the physico-chemical properties (water activity, water holding capacity, water binding capacity, hydration and gelation properties) of the two different CTW (Longe 1984). The two samples were then steamed for 30 minutes in a steaming pot after which they were brought out to cool and emptied into previously sterilized fermentation trays measuring 54cm x 38cm x 4cm for the length, width and depth respectively. The trays were underlain with transparent cellophane sheets which also doubled as the sheet with which the wastes were covered [,Photo 3].

The steam-sterilized samples were inoculated with a consortium of lactic acid bacteria (L. delbrueckii and L. coryneformis) and a fungus (Aspergillus fumigatus) in a lamina flow chamber. 60mls of a combination of L. delbrueckii and L. coryneformis containing 1.2 x 10⁴ cells/ml and 80mls of the fungal suspension containing 1.07x10⁷spores/ml were used to inoculate the two CTW samples [,Photo 4]. These two samples were thereafter kept in fermentation chambers [,Photo 5] to ferment for five days. They were subsequently sundried and stored for chemical analysis. These samples fermented with selected micro-organisms were designated microbially fermented cassava starch residues (MFCSR) and microbially fermented cassava peels (MFCP) respectively.  

Photo 3: The cellophane wrapper device that ensures the maintenance of optimum water activity within the fermenting substrates. Visible are the refluxing water droplets.	Photo 4: Mixing the microbial inoculums with sterilized cassava peel sample	Photo 5: Fermentation chamber opened to show the arrangement of fermentation trays within the chamber.

Chemical analyses

Proximate analyses were carried on triplicate samples of the six differently processed CTW for moisture, crude protein, crude fibre, ether extract and ash as described by the methods of AOAC (1995). The neutral detergent and acid detergent components of the fibre (i.e. NDF and ADF) were analyzed by the methods described by Van Soest (1991) while the metabolizable energy (ME) was calculated from Pauzenga (1985) formula as follows:

ME (kcal/kg DM) = (37 x % CP) + (81.8 x % fat) + (35.5 x % NFE)

Determination of the amino acid profile of the fermented and unfermented cassava tuber wastes.

The amino acid profile of the variously processed CTW samples was determined using the methods described by Speckman et al (1958). Triplicate samples of these wastes were dried to constant weight, defatted, hydrolyzed, evaporated in a rotary evaporator and loaded into the Technicon Sequential Multi-sample (TSM) Amino Acid Analyzer.

Statistical analysis

A Completely Randomized Design was used to analyze data obtained from the experiment. The results were presented as mean values of three replicates each. One way analysis of variance (ANOVA) and Duncan multiple range tests were carried out using SAS (2000) Statistical Package. Significance was accepted at P≤0.05. 

Results and Discussion

Proximate composition of the fermented and unfermented CTW: Table 1 shows the proximate composition of the six treatment samples of both the CSR and CAP.  

The moisture content of the CTW samples decreased with fermentation and more so in the samples fermented with selected micro-organisms. This decrease could be attributed to the fact that the micro-organisms utilized the substrates moisture for growth thereby reducing the samples’ moisture content (Raimbault and Alazard 1980) while at the same time increasing their dry matter content.  The crude protein was significantly improved in all the microbially fermented samples. This increase was from 1.12g/100g in the UFCSR sample to 7.02g/100g in the MFCSR samples. The crude protein content in the cassava peels increased from 5.30g/100g in the UFCP to 10.9g/100g in the MFCP samples. These micro-organisms by implication thus offered a variety of possibilities for protein enhancement in agro-industrial by-products as reported by Manilal et al (1987). The increase in protein content of the samples fermented with micro-organisms could be due to the possible secretion of some extra-cellular enzymes (proteins) such as amylase, linamarase and cellulase (Oboh and Akindahunsi 2003) into the CTW by the micro-organisms in an attempt to make use of these wastes as a source of carbon (Raimbault 1998). The highest protein content obtained with the microbial fermentation of the CSR samples in this study conformed to the value of 7.0% reported by Balagopalan and Padmaja (1988).

The CTW samples generally have high crude fibre content. The values obtained for the CSR were 19.2g/100g, 12.9g/100g and 12.1g/100g for the UFCSR, NFCSR and MFCSR respectively while 38.4g/100g, 8.72g/100g and 5.88g/100g were obtained for the UFCP, NFCP and MFCP samples respectively. The UFCP samples thus had the highest crude fibre value, also the trend of observation showed that microbial fermentation led to a significant (P<0.05) decrease in the crude fibre content of all the samples with varying degrees depending on the strength of the crude fibre degradability of the organisms in the different fermenting substrates  (Bakrie et al 1995). This same trend was also observed in the ADF and NDF components of the crude fibre. The decrease in crude fibre content of these samples by the action of the micro-organisms could therefore enhance digestibility in the animals’ gastro-intestinal tracts if these fermented wastes are eventually included in livestock ration formulation.

The ash content ranged between 2.74g/100g and 4.15g/100g for the CSR samples and from 4.15g/100g to 6.62g/100g for the CAP samples. A slight but significant (P< 0.05) increase was observed in the two fermented CSR samples over the UFCSR sample, but fermentation led to an increase in the NFCP but a decrease in MFCP samples. The increase in the ash content of the fermented CTW could have been as a result of the hydrolysis of such chelating agents like phytate which is highly concentrated in cassava waste products (Aro et al 2010) The trend observed in the ash content of the cassava peel (CAP) samples was at variance with the report of Oboh and Akindahunsi (2003) who reported an increase in the ash content of cassava peels as a result of microbial fermentation. The difference in the observed trend in this study and that of Oboh and Akindahunsi (2003) could be attributed to the nature of the cassava peels used in the two studies. Factory-processed CAP with a higher crude fibre, no adhering pulps and lower soluble carbohydrates content was used in this study as opposed to the hand-processed CAP with lots of adhering pulps, higher soluble carbohydrates and lower crude fibre that was used by the other authors. The higher soluble carbohydrates made available to the micro-organisms thus permits higher accumulation of biomass with a concomitant accumulation of ash deposited by micro-organisms in the fermenting substrates. This same argument could be advanced for the increase in the ash content of the CSR samples with fermentation because of their comparatively lower crude fibre content and hence a higher propensity for biomass accumulation and ash deposition within the fermenting substrates.

The values for the ether extract were 2.03g/100g, 2.23g/100g and 3.97g/100g for the CSR samples and 2.98g/100g, 3.11g/100g and 3.12g/100g for the CAP samples. Samples with microbial inoculums showed that an enhancement in fat content has been brought about as a result of fermentation. Oboh and Akindahunsi (2003) obtained similar results in their work with the same type of bacteria but without the fungus on cassava peels. The increase in fat content of the fermented samples might not be unconnected with the biosynthesis of lipids during the fermentation process by the micro-organisms from the available carbohydrate sources in these CTW they fed upon while the fermentation process lasted.

The NFE values varied significantly among the six CTW samples. The NFE value was generally very low in the unfermented CAP samples. This may not be unconnected with the high crude fibre content of the factory-processed cassava peels. The range of values of NFE obtained for CSR in this trial (72.8-74.8g/100g) was better than the value of 55-70% reported by Devendra (1977). The higher NFE content in this trial could have been brought about by microbial fermentation which broke the crude fibre component in the CTW into soluble carbohydrate units through enzymatic hydrolysis.

The amino acid profile of the CTW is as shown in Table 2. The fermented CTW samples showed significant improvement in amino acid profile over the unfermented samples.

 The NFCSR had the best amino acid enhancement among the six differently processed CTW samples and the best for the essential amino acids like Lysine (3.28g/100g), Valine (3.98g/100g), Leucine (7.17g/100g) Isoleucine (3.23g/100g), Arginine (4.43g/100g) and Threonine 3.14g/100g). The MFCP samples had the best enhancement in terms of Methionine (0.89g/100g), Cysteine (1.06g/100g) and Phenylalanine (3.89g/100g). Ezekiel et al (2010) reported similar enhancement of cassava peel subjected to submerged fermentation with the fungus – Trichoderma viride. The possibility of nutrient enrichment of highly fibrous and protein-deficient agricultural wastes as reported in literature (Soccol et al 1994; Tewe 1996; Aro 2008) has been further reinforced by the results of this trial.

Conclusion

• This trial revealed the possibility of nutrient enrichment of two erstwhile underutilized cassava tuber wastes through microbial fermentation. The increase in protein and energy contents of these wastes is comparable to those of maize and this would mean they could be used as perfect replacements of maize in any practical livestock diets. Subjection of these wastes to fermentation would really help to beef up the protein quality as seen in the increase in the amino acid content of the fermented products. The ability of the micro-organisms to degrade crude fibre component of CTW especially of cassava peels is also noteworthy. Further research on this combination of micro-organisms is suggested to elucidate any synergy or synchrony in their ability to biodegrade crude fibre component of cassava products and possibly of any agro-industrial wastes.

Acknowledgement

The authors are grateful for the financial support received from the University Research Grant No: URGC/MAJOR/2007/180 of the Federal University of Technology, Akure, Nigeria.

References

AOAC 1995 Official method of analysis of the Association of Official Analytical Chemists. 16^th Ed. Arlington, Virginia, U. S. A.

Aro S O 2008  Improvement in the nutritive quality of cassava and its by-products through microbial fermentation. African Journal of Biotechnology. 7(25): 4789-4797.

Aro S O 2010 Growth and reproductive response of swine fed fermented cassava tuber wastes. Ph.D Thesis. University of Ibadan, Ibadan, Nigeria. Pp. 176.

Aro S O,  Aletor V A, Tewe O O and Agbede  J O 2010 Nutritional potentials of cassava tuber wastes: A case study of a cassava starch processing factory in south-western Nigeria. Livestock Research for Rural Development. Volume 22, Article #213. Retrieved January 9, 2011, from http://www.lrrd.org/lrrd22/11/aro22213.htm

Bakrie B, Hendra J and Nazar A 1995  Effects of using different techniques in bio-process to the nutritive value of cassava leaves. Proc. of XI National Biology Seminar. University of Indonesia, Jarkata.

 Balagopalan C and Padmaja G 1988 Protein enrichment of cassava flour by solid substrate fermentation with Trichoderma pseudokonigii ritai for cattle feed. In: Proceedings of the 8^th symposium of the International Society for Tropical Root Crops. Bangkok. Oct. 30-Nov. 5, 1988: 426-432.

Devendra C 1977  Cassava as a feed source for ruminants. In: Cassava as animal feed. (Eds., Nestel, B. and Graham, M.). Proceedings of Workshop. University of Guelph. IDRC-095e, 107, Ottawa.

Ezekiel O O, Aworh O C, Blaschek A P and Ezeji T C 2010 Protein enrichment of cassava peel by submerged fermentation with Trichoderma viride (ATCC 36316). African Journal of Biotechnology. 9(2): 187-194.

Gow-Chin Y, Horn-Wen  C and Pin-Der D 1998 Extraction and identification of an anti-oxidant component from Jue Ming Zi (cassava tora L.). Journal of  Agriculture and Food Chemistry 46: 820-824.

Israelides  C  J,  Smith  A,  Harhill J E, Bambalor G and Scallon B 1998  Pullulan content of the ethanol precipitated from fermented agro-industrial wastes. Applied Microbiolgy and Biotechnology. 49: 613-617.

Iyayi E A, Tewe O O and Oki R T 1997 Processing cassava leaves for broiler production in South West Nigeria. Nationally Coordinated Research Project (NCRP53), University of Ibadan.

Longe O G 1984 Water holding capacity of some African vegetables, fruits and tubers measured in-vitro. Journal of Food Science 49: 762-764.

Manilal V B, Narayanan C S and Balagopalan C 1987 Amyloglucosidase and cellulase activity of Aspergillus niger in cassava starch factory wastes. Tropical Tuber Crops Production and Utilization. Indian Society for Root Crops, CTCR, Trivandrum, India: 211-213.

Nwafor O E and Ejukonemu F E 2004 Bioconversion of cassava wastes for protein enrichment using amylolytic fungi. A preliminary report. Global Journal of. Pure and Applied Sciences. 10: 505-507.

Oboh G and Akindahunsi A A 2003 Chemical changes in cassava peels fermented with mixed culture of Aspergillus niger and two species of Lactobacillus integrated bio-system. Applied Tropical Agriculture. 8: 63-68.

Pauzenga U 1985 Feeding Parent Stock. Zoo Technical International. Pp. 22-24.

Raimbault M 1998 General and microbiological aspects of solid substrate fermentation. Electronic Journal of Biotechnology. 1(3): December, 1998.

Rainbault M and Alazard D 1980 Culture method of studying fungal growth in solid fermentation. European Journal of Applied Microbiology and Biotechnology. 9: 199-209.

SAS Users’ Guide: Statistical Analysis Systems  2000 Institute Inc. Cary. North Carolina, U.S.A.

Soccol C Marin B  Raimbault M and Lebeault  J M 1994 Breeding and growth of Rhizopus in raw cassava by solid state fermentation. Applied Microbiology and Biotechnology. 41: 330-336.

Speckman D H, Stein E H and Moore S 1958 Automatic recording apparatus for use in the chromatography of amino acids. Analytical Chemistry. 30: 1191.

Sucharita S,  Makkar H P S and Becker K 1998 Alfalfa saponins and their implications in animal nutrition. Journal of Agriculture and Food Chemistry 46: 131-140.

Tewe O O 1996 Enhancing the nutritive value of cassava for livestock feeding through microbiological degradation. Paper presented at the 3^rd International Scientific meeting of the Cassava Biotechnology Network (C.B.N.III) Kampala, Uganda, 27-1996.

Van Soest  P  J,  Robertson J B and Lewis B A 1991 Methods of dietary fibre, neutral detergent fibre and non-starch polysaccharides in relation to animal nutrition. Journal of Dairy Science. 74: 3583-3597.

Received 26 January 2012; Accepted 25 February 2012; Published 4 March 2012

Go to top