Abstract:
Groundnut (Arachis hypogea) is an important oil seed crop in Nigeria. The pulp or dry pericarp contains about 25-40 percent shell. Large amount of lignocellulosic waste is generated through agricultural practice and they are of environmental concern. Microorganisms play a lot of roles in the environment, one of such roles is the degradation of waste and hence remediation of the environment. Biodegradation offers a cheaper method of converting the agricultural residues into usable forms such as fermentable sugars that could be used for the production of other value added products. This work was aimed at evaluating the potential of some fungal isolates in degradation of groundnut shells to fermentable sugars. Fungi were isolated from steeped groundnut shells for 3-6 weeks; the isolated fungal were screened for their ability to degrade groundnut shells to fermentable sugar. Effect of substrate concentration (5 - 20g), nitrogen sources (yeast extract, NaNO₃, peptone, soya-bean meal and NH₄H₂PO₄) and pH (3- 9) on the degradation of groundnut shells by fungal isolates were evaluated. The isolates were identified tentatively as Aspergillus sp.1-3 and Trichoderma sp. It was observed that the nitrogen sources used influenced the sugar yield by the organisms as Aspergillus sp. 3 gave the highest glucose yield of 15.7g/l with NaNO₃ while Aspergillus sp 1, Trichoderma sp and Aspergillus sp 2 have their best source of nitrogen as soyabean meal with yields 7.5g/l, 9.8g/, and 8.6g/l respectively. Effect of substrate concentration showed that there was an increase in glucose yield with increase in substrate concentration, Aspergillus sp 1, gave the highest glucose yield of 51.9 g/l with 20g substrate concentration followed by Aspergillus sp 3 glucose yield of 43.3g/l In Aspergillus spp 2, 15g substrate concentrate gave the highest glucose of 42.2g/l. pH 5 was optimal for the degradation of groundnut shells . When compared the degradation of groundnut shells using all the four fungal in synergy a glucose yield of 58.7g/l was obtained at pH 5, 15g substrate concentration and Peptone as the best nitrogen source. The cellulose used by the fungal were estimated, Co-culture was able to degrade the highest amount of cellulose content of the groundnut shells by degrading 65% followed by Aspergillus sp 1 59%, then Aspergillus sp 3 54.5%. Aspergillus sp 2 with 52.9% and Trichoderma sp 48.8% this study has shown that the use of the fungal in co-culture resulted to improved biodegradation and hence higher yield of fermentable sugars.
