Aspergillus niger isolated from rotting cassava produced raw starch degrading amylase on cassava, maize, sorghum and soluble potato-derived starch as the sole carbon source without prior gelatinisation. Maximum activity of the amylase was attained using cassava starch as substrate. The crude enzyme solution which comprised a mixture of raw and non raw starch digesting amylase degraded both cereal and tuber or root starches significantly. Source of assay starch significantly influenced raw starch digesting activity. Optimum pH for the raw starch degrading and the extracellular amylase were 6.0 and 3.5-4.0, respectively. However, both enzyme activities appeared t o be uninfluenced across a relatively broad pH range 3.0-7.0. N o correlation was found between the capacity of starch to induce expression of the enzyme and its susceptibility to enzyme digestion. The adsorbability of the various starches to raw starch digesting amylase was directly related to their digestibility.
In the present study solid waste were collected from households, banks, restaurants, higher institution, open dump and a final disposal site of Nigerian municipality with a view to determining waste generation rate, relative waste compositions and its physicochemical properties. During the course of study average rate of solid waste generation was found to be 0.39Kg/capita/day. A highly negative correlation (R2 = 0.99) was observed between per capita waste generation and household size (n) for n ? 4. The waste collected from households consisted of putriscibles (47%) 11% water proof, 6% plastics, 4% glass, 3% clothes/textiles, 2% diapers and 19% of other unclassified materials. Due to the activities of scavengers, the relative proportion of recyclables such as plastic, glass and metals decreased as waste materials transited from households to the final dumpsite via open dumps, while the other fractions increased. It was found that 79% of the solid waste generated can either be recycled (32%) or composted (47%) however; only 12% is recovered for recycling/reuse while composting is hardly practiced. The three most important factors responsible for relative differences in the composition of solid waste obtained from different sources are scavenging, biodegradation and leaching. The putriscible fractions from households, curb sides and the final disposal site were assessed for their suitability for composting using the clean index (CI) criteria. It was found that the final disposal site with a CI of 3.3 on a scale of 5 was a better source of compost material than freshly generated household waste (CI = 2.9) and curb side waste (CI = 2.4).
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