Biological Wastes最新文献

Although the recycling of excrements in integrated agriculture-aquaculture farming systems offers many advantages, the spread of diseases to man via aquatic organisms multiplying in excreta-laden water needs special attention. There is strong evidence that aquatic organisms may be more important vectors for human diseases than generally realized. However, conclusive epidemiological studies linking the use of excreta in aquaculture with human diseases are lacking.

Soda-AQ pulping of sorghum stalks increased the rate of delignification and the pulp yield and improved the strength properties compared to soda pulping, but the effect of AQ addition (0·13% on oven-dry raw material) was less pronounced than for tropical hardwoods. The wet-depithing of the stalks contributed considerably to the yield and strength properties, while the alkali consumption and rejects were decreased. Addition of guar gum (0·5% on oven-dry pulp), after beating, as wet-end/dry-strength agent, improved the drainage and strength properties. The soda-AQ pulping makes pulping of sorghum stalks much more attractive and feasible, once the other technical constraints are overcome by employing the recent techniques developed for other agricultural residues.

The increasing size of poultry processing plants has intensified the problem of disposal of poultry wastes, mainly offals and feathers. Processing of this waste as a feedstuff will play a part in solving the world's protein needs by producing more animal protein and creating a price structure. Raw feathers are not digested by animals. Processing them by means of pressure ranging from 207 to 690 kPa, time ranging from 6 to 60 min and moisture ranging from 60 to 70%, will break down their keratinous material, resulting in a hydrolized feather meal with a 70% digestible crude protein. Processing is at present achieved by batch cooker, continuous processing, or high shear extruding. Time, pressure, humidity and agitation affect the nutritive value of the hydrolized feather meal. Some additions, such as synthetic amino acids, methionine, lysine, fish meal, dried whey powder, to hydrolized feathers in diets or to poultry offal during processing will increase the nutritive value of this product. Hydrolized feather meal may be added up to 6% of the ration for broilers, 7% for layers and 5% for turkeys in well balanced diets, without harmful effect as far as production or health are concerned.

Common carp fed over a period of 140 days on diets containing different levels of non-defatted pupae showed better growth with the diet containing 30% papa, without fish meal. Ten per cent and 20% of pupa in combination with 20% and 10% fish meal gave lower growth, although statistically there was no difference between different treatments. Digestibility of protein and fat from pupa diets was better than that from the fish meal control diet. Significantly higher deposition of protein, fat and ash was recorded with diets having 20% and 30% pupa. Experimental diets had no influence on organoleptic quality in terms of colour, odour, texture and flavour. The results show that non-defatted pupa could replace fish meal in the diet of common carp, without affecting growth and quality.

The maximum growth rate (μ_m) of acetoclastic methanogens was measured at ammonia concentrations between 0·55 and 0·74 mol/liter (7·7 and 10·4 g ammonia-N/liter) and a pH between 7·80 and 7·93. The observed μ_m varied between 0·0046 and 0·0000 h⁻¹ under these experimental conditions. The μ_m was calculated by monitoring the gas production rate of batch reactors under conditions of substrate saturation (maximum growth rate in prevailing environment); the acetate concentration during all experiments was above 0·025 mol/liter (1·5 g/liter). It was shown that the pH and total ammonia concentration are the predominant inhibition factors for acetoclastic methanogens under these conditions. The best mathematical description for the inhibition of the growth rate is given by an equation which contains the total ammonia concentration as well as the pH, and this description was significantly better than a description using a calculated free ammonia concentration. The results can be used to calculate a minimal hydraulic retention time for acetate degradation in poultry manure digesters.

During studies on ‘Refuse Recycling Processes in Karachi’ for the United Nations Centre for Human Settlement (UNCHS-Habitat), a chemical evaluation of organic putrescible matter, a major component of recyclable materials, was carried out. The average putrescible matter (after sorting) had pH 6·1; moisture 39·5%; organic matter 56%; carbon 34%; nitrogen 1·2%; and C/N 28. These figures are in conformity with the optimum values needed for aerobic composting and hence this portion of refuse is a suitable material for bioconversion.

The earthworm Eisenia fetida, known to contain bactericidal enzymes, was tested for virucidal activity using Cowpea mosaic virus (CPMV) and Tobacco mosaic virus (TMV) as model agents. Earthworms were fed cellulose saturated with a virus suspension and their excreted castings were analyzed for structurally intact virus protein using enzyme-linked immunosorbant assay (ELISA) and virus infectivity by local lesion assays. Observations of the feeding experiments indicated a considerable reduction in the infectivity of both viruses. Virucidal activity was also observed when virus suspensions were incubated with the earthworm enzyme extract and analyzed by local lesion assay. The observed reductions in the infectivity of both viruses suggest that E. fetida may possess a virucidal enzyme system and, accordingly, may contribute to the inactivation of pathogenic viruses potentially associated with land application of sewage sludges and livestock manures.

The utilization of methanol or mango-waste hydrolyzate by Pichia pinus was studied with respect to the biomass, single cell protein and other metabolites. Optimum cultural conditions on both substrates were 30°C and pH 4·8–5. The maximum yield was obtained at the third day of growth (3·6 g/litre in methanol medium, 6·2 g/litre in mango-peel extract medium). At the end of the logarithmic phase, methanol yeast cells contained 52·2% crude protein, 36% true protein and 14·2% nucleic acids, while cells grown on mango-peel extract contained 62·2% crude protein, 39% true protein and 12·9% nucleic acids. The amino acid composition of the protein, especially of the essential acids, was comparable to FAO standards. α-Ketoglutaric and pyruvic acids were found in cells from both substrates but dihydroxyacetone was found in high quantity in methanol medium (976·9 μg%) while acetoacetic acid was found only in mango-peel medium (244·4 μg%).