Enhancing the biodegradation process of cassava (Manihot esculenta Crantz) peels in dump site

Cassava (Manihot esculenta Crantz) peels have been implicated in serious environmental pollution. This study was aimed at investigating the effect of N.P.K (15:15:15) and microbial inoculants on the biodegradation process of cassava peels. Fresh cassava peels were subjected to biodegradation process for twenty weeks. The process was monitored by determining the moisture content, starch and total lipid using the official method of analysis of A.O.A.C, total protein by Kjeldahl method, total soluble carbohydrate by the modified Anthrone method, cellulose by the Nitric acid method, total cyanide by the modified alkaline picric acid method and pH using a Jowrey 3020 pH meter. The results of unsupplemented cassava peels and cassava peels supplemented with inorganic fertilizer N.P.K. (15:15:15) in experimental waste dump sites in which combinations of pure microbial cultures were used to inoculate cassava peels showed that pH increased from 5.89 to 7.03, total soluble carbohydrate concentrations decreased from 2.23% to 0.02%, protein from 5.54% to 0.78%, lipids from 3.00% to 0.1%, starch from 9.65% to 0.02%, cyanide from 0.11% to non-detectable level and cellulose from 8.80% to 0.20% at the end of the 20 weeks of investigation. This is an indication that the addition of inorganic fertilizer or microbial inoculants, or both enhanced the rate of biodegradation of cassava peels.


Introduction
turn of the 20 century has increased to the point Economic difficulties in Nigeria since the last where natural mechanisms for accomplishing their three decades have resulted in the high demand for degradation are no longer efficient and therefore cassava products such as garri, lafun, fufu, santana causing their accumulation (USEPA, 2005).and tapioca as they are cheap sources of energy.The Cassava peels which are the major waste increased demand for cassava has resulted in an from cassava, are either dumped indiscriminately in a increase in annual cassava peels generated over the Landfill/waste dump or refuse dump where they years.It was estimated that Nigeria produced remain as huge mounds.In spite of its good between 34 to 40 million metric tons of cassava tubers nutritional components which include protein, fat, in the year 2005 and 2.96 million metric tons of carbohydrate, minerals, water and fibres (Morgan and cassava peels (Aro et al., 2010), while in 2006Nigeria Choct, 2016), the high level of cyanide and tannin has produced 45.7 million metric tons of cassava (Sanni et limited its usage (Ofuya and Obilor, 1994).Pondja et al., 2009) and 54.4 million metric tons in 2011 (Elemo, al. (2017) reported the removal of cyanide from 2013).Cassava processing produce large amounts of cassava peels through fermentation and the waste and is generally considered to contribute subsequent application of the fermented cassava significantly to environmental pollution (FAO, 2001).peels for treatment of mine water in a laboratory Globally, the amount of waste generated since the scale.
The problems associated with the Physico-chemical parameters accumulation of cassava peels in waste dumps are T h e p h y s i c o -c h e m i c a l p a r a m e t e r s pollution resulting from either the slow microbial determined were moisture contents, starch and total degradation or burning of the peels or both, washing lipid using the Official method of analysis of A.O.A.C of the decomposing peels into nearby surface water (1990).Total protein was by the method of Kjeldahl as and ground water and pollution resulting from described by Bradstreet (1965), total soluble diffusion of the leachates from the partially carbohydrate by the modified Anthrone method decomposing peels into ground water.In order to described by Clegg (1956), Cellulose by the Nitric acid address these problems, this study was designed to method of Kurschner and Hoffner modified by enhance the biodegradation process of cassava peels Okhamefe et al. (1991), total cyanide content was in waste dump by introducing inorganic fertilizer determined by the modified alkaline picric acid N.P.K. (15:15:15) and pure cultures of cassava peelmethod of Ikediobi et al. (1980) and pH was degrading microorganisms.monitored using Jowery 3020 pH meter.All chemicals used were of analytical grade.

Collection of materials
Enumeration and isolations of microorganisms Fresh cassava peels were collected from Total aerobic microbial count was determined women peeling cassava tubers for garri processing on cassava peel agar medium (CPAM), which was and a waste dump in the school of supply and prepared by adding 15g of Agar agar (Oxoid) to transport (S & T Army Baracks) off Uselu-Lagos Road, 1000ml of cassava peel extract prepared by adding Benin City and stale cassava peels were collected from 50g of ground fresh cassava peels to 1000ml of a waste dump site at S & T Army Barracks off Useludistilled water.This was later stirred (after 10min) and Lagos Road, Benin City.
filtered through a cheese cloth to obtain a filtrate known as the cassava peels extract.The CPAM Waste site preparation prepared was homogenized and thereafter sterilized 0 Four experimental waste sites, each of about by autoclaving at 121 C for 15min.Bacteria counts 1meter by 1.15 meters were set up.They were were on CPAM containing 10mg nystatin to inhibit designated sites A, B, C and D and were 30 meters growth of fungi while fungi counts were on CPAM apart from one another in the same environment.Site containing 0.5g chloramphenicol to inhibit bacteria A contained cassava peels and inorganic fertilizer growth.All plates for bacteria counts were incubated 0 [N.P.K. (15:15:15) (0.5%)], site B contained cassava at 37 ± 2 C while plates for fungal counts were 0 peels and microbial inoculates (pure cultures of incubated at room temperature (28±2 C). bacteria and fungi isolated from stale cassava peels obtained from the waste dump site), site C contained Characterization and identification of Isolates cassava peels, microbial inoculants and inorganic The bacterial isolates were characterized and fertilizer and site D which is the control contained identified according to the methods outlined by cassava peels only.Collins and Lyne (1984) and Don et al. (2005).The Cassava peels at sites A, B, C and D were moulds isolates were identified by the method exposed to the same environmental conditions.In a outlined by Barnett and Hunter (1972) and Domsch et bi-weekly basis, samples (triplicate) were collected al. (1980), while the yeast isolates were characterized for physiochemical and microbiological analysis.
by the method outlined by Rhode and Hartman These include total protein, pH, moisture content, (1980) andLodder andKreger-Van Rij (1984).starch, total lipid, soluble carbohydrate, cellulose, total cyanide content and isolation of microorganism Results and Discussion involved in the degradation of cassava peels.
The results of the analysis of physio-chemical parameters of the cassava peels undergoing biodegradation are shown in Tables 1 to 8. Results are mean value of three samples collected from the same site.The results in Table 1 show the variation of A, B and C.This shows that although bioremediation total protein in the cassava peels with biodegradation process took place in the control but at a much slower time.Between week 0 and week 6, the total protein rate.Akinyele et al. ( 2011) attributed this increase in increased from 5.54% to 16.80%; 16.80%, 18.80% total protein in cassava peels undergoing and 11.80% for sites A, B, C and D respectively.decomposition to the high number of microorganisms However from week 6 to week 20 the total protein with the ability to secrete certain extracellular decreased to 0.2%, 0.4%, 0.78% and 0.2% for sites enzymes such as amylase, cellulase and linamerase A, B, C and D. The increase in the total protein content involved in their metabolism.The results of this study of the cassava peels during biodegradation could be were similar to the one obtained by Ofuya and attributed to the growth of the microorganism that Nwajiuba (1990).They stated that there was increase were involved in the degradation processes as in the crude protein content of cassava peels from indicated in the result in sites A and B which are 5.6% to 16% after 120 hours of fermentation.The biostimulation and bioaugumentaiton processes gradual decrease in the protein content of the cassava respectively.However, in site C which contained peels from week 6 could have resulted from the microbial inoculants and N.P.K which also enhanced buildup of toxic microbial metabolites, which might the growth of the microorganisms, there was a more have caused the death of some of the microorganisms appreciable increase in total protein.The control in responsible for the degradation and this was site D without microbial inoculants and N.P.K. showed experienced in all the sites.a lower total protein content when compared to sites

Table 2: Variation of pH in cassava peels with biodegradation time
The variation of pH in cassava peels with microorganisms that make use of the components of biodegradation time are shown in Table 2.There were the cassava peels for their own growth and release gradual decline in pH in all the sites from week 0 to organic acids as by products which led to the decrease week 10, that is from 5.89 in week 0 to 4.51, 4.41, in the pH.Ofuya and Nwajiuba (1990) reported a drop 4.21 and 4.64 in sites A, B, C and D respectively.This in the pH from 5.6 to 4.4 after 120 hours of cassava can be attributed to the biodegradation activities of peels fermentation.
There were decreases in the moisture as evaporation of moisture from the cassava peels as content of the cassava peels in all the sites (A, B, C well as the water used by the microorganism for and D) from week 0 to week 20.These decreases growth thereby reducing the moisture content of the might have resulted from the exposure of the cassava cassava peels.peels to the prevailing environmental conditions such  (2004) attributed the decrease in carbohydrate to the fact that the soluble carbohydrate served as content to the conversion of Oligosaccharides to source of carbon for the growth of the simple sugars or the utilization of the carbohydrate as microorganisms involved in the biodegradation source of energy by the fermenting microorganisms process.The almost complete usage of soluble for growth and metabolism.carbohydrate in site A, B and C shows that the rate of The variation of starch content in cassava site C due to the fact that the inorganic fertilizer added peels with biodegradation time are shown in Table 5.
helped to stimulate the degradation abilities of the Although there were decreases in the starch content few microorganisms in the environment that came in in all the sites, the decrease in site C was highest as it contact with the cassava peels and thereby use both decreased from 9.65% to 0.02%, this was followed by the nutrient in the cassava peels and the inorganic site B which decreased to 0.15%, site A decreased to fertilizer to enhance their growth.Site D had the least 1.00 and site D decreased to 3.00%.The decrease reduction in starch content due to the fact that the observed in site C can be attributed to the fact that the biodegradation process in it was slow because it was biodegradation abilities of the microorganisms in this neither enhanced by the addition of inorganic site were enhanced by the inorganic fertilizer that was fertilizer nor the addition of pure cultures of cassava added.This was followed by site B, where the peel degrading microorganism.Similarly, Adamafio et metabolic activities of the microorganism also led to al. ( 2010) reported a decrease in the starch content of the reduction observed.The reduction in the starch cassava peels fermented for 7 days.content of site A was not as high as that of site B or The cellulose content in the cassava peels the activities of the microbial inoculants were not were varied with biodegradation time as shown in enhanced so the decrease in the cellulose content Table 6.There were gradual decreases in the cellulose were not as much as that in site C.The decrease in content of all the sites, from week 0 to week 20.At the site A was a little lower than that in site B due to the end of week 20 the least decrease was observed in few microorganisms from the environment that were site D while the highest decrease was observed in site enhanced by the inorganic fertilizer.The least C. It is obvious that the microbial inoculants in site C decrease in site D is as a result of slow process of which were enhanced by the addition of inorganic natural degradation.Ofuya and Nwajiuba (1990) fertilizer produced cellulase enzyme which rapidly reported a similar decrease in the cellulose content of degraded the cellulose in the cassava peels.In site B, cassava peels during solid state fermentation.
Total lipids in the cassava peels were varied utilize lipids for their own growth.Adamafio et al. with biodegradation time as shown in Table 7.The (2010) reported significant decreases in fat content of decrease in total lipid during the study in all the sites cassava peels fermented for 7days.The least decrease might be due to the microorganisms (both those from was still observed in site D. the environment and inoculants cultures) ability to  8. Cyanide ascribe cyanide degradation in cassava peels to is one of the products released when the cynogenic contact between the enzyme linamarase and the glycoside linamarine is hydrolyzed by the enzyme cyanogenic glycoside.Kandasamy et al. (2015) linamarase.Linamarin, which is localized in the cell reported the utilization of cyanide as a nitrogen vacuole easily come in contact with the enzyme source by some bacteria.linamerase as a result of disruption of the cellular Results obtained from the physio-chemical integrity of the cassava peels.The action of parameters determined for the experimental waste microorganisms actually accelerated the entire site showed that the addition of inorganic fertilizer processes leading to the degradation of cassava N.P.K. (15:15:15) or microbial inoculants or both peels.The results in Table 8 showed that the decrease enhanced the rate of biodegradation of cassava peels. in cyanide concentration in cassava peels in sites A, B Some of the microorganisms isolated from and C at the end of the fourth week were similar.The cassava peels undergoing biodegradation in the cyanide concentration in these sites were less than present study have been shown to be involved in 0.5mg CN/kg fresh weight.However, site D which cassava peels fermentation (Adeleke et al., 2017), contained cassava peels only still had over 65mg while other researchers showed their involvement in CN/kg fresh weight at the end of the fourth week.This the processing cassava tubers for garri production simply shows that the addition of microbial inoculants (Zvauya and Muzondo, 1995;Blanshard et al., 1994; increased the rate of contact between the enzyme Ray, 1995).Since the peels have been shown to linamarase and it's substrate linamarin.The addition contain the same components as the cassava tuber, of inorganic fertilizers further increased the activities although richer in some of the component such as of the microorganism involved in the degradation of protein (Aro, et al., 2010), it is not surprising that the cassava peels, this is why there were no more cyanide microorganism isolated (Table 9) during the in site C at the end of the sixth week.Njike et al.
biodegradation of the peels are the same as those (2014) reported that the eradication of cyanide from involved in the fermentation of cassava tubers.cassava peels is due to cyanide contact with

Table 7 : Variation of total lipids in cassava peels with biodegradation time Table 8: Variation of total cyanide in cassava peels with biodegradation time
The variation in total cyanide in cassava peels linamarase.Similarly, Asegbeloyin et al. (2007) with biodegradation time is shown in Table