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Protein generation and delignification of alder sawdust by thermophilic microorganisms Wolde-Tsadick, Maheteme Selassie

Abstract

It has been indicated through a review of the literature that wood by-products have a potential as a dietary source of energy for the ruminant animal. However, lignin constitutes a barrier to the proper utilization of cellulose. Generally, any treatment to remove or alter lignin makes the cellulose within lignocellulose materials more susceptible to the activity of the cellulolytic enzymes. Therefore, an efficient biological treatment would require a system to solubilize or to remove lignin from the lignin-carbohydrate complex. Cellulose within ruminant feeds forms an effective substrate for eventual conversion to body protein. There are several methods available for delignification. This study was carried out using the thermophilic aerobic oxidation method for which swine manure was used both as the source inocula and initial culture media. In the process of degradation, a part of the energy produced was utilized by the bacteria for cell function and multiplication. The remainder of the available energy was released as heat energy. In this method the heat necessary to maintain the temperature in the thermophilic range was derived from both mechanical and from microbial activity. Thermophilic activity is considered to reduce the time required for organic waste digestion over that experienced by mesophilic digestion. The rate of the destruction of pathogenic bacteria, virus and other organisms is increased as a result of the high temperatures fermentation. Batch studies conducted to delignify alder sawdust by the use of the aerobic thermophilic oxidation method demonstrated that the lignin content of sawdust can be reduced by as much as 74%, and crude bacterial protein was generated by approximately 17%. Constant supply of small amounts of swine manure ensures high temperature maintenance. Periodical addition of 2 kg sawdust within thermophilic temperature range results in better delignification.

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