Single cell protein

Description: 

Single cell protein has the potential to be developed into a very large source of supplemental protein that could be used in livestock feeding. In some regions single cell protein could become the principal protein source that is used for domestic livestock, depending upon the population growth and the availability of plant feed protein sources. This could develop because microbes can be used to ferment some of the vast amounts of waste materials, such as straws; wood and wood processing wastes; food, cannery and food processing wastes; and residues from alcohol production or from human and animal excreta. Producing and harvesting microbial proteins is not without costs, unfortunately. In nearly all instances where a high rate of production would be achieved, the single cell protein will be found in rather dilute solutions, usually less than 5 % solids. Methods available for concentrating include, filtration, precipitation, coagulation, centrifugation, and the use of semi-permeable membranes. These de-watering methods require equipment that is quite expensive and would not be suitable for most small-scale operations. Removal of the amount of water necessary to stabilize the material for storage, in most instances, is not currently economical. Single cell protein must be dried to about 10 % moisture, or condensed and acidified to prevent spoilage from occurring, or fed shortly after being produced.

Caution: 

Microbial protein has a high nucleic acid content, so levels need to be limited in the diets of monogastric animals. Some organisms can also produce mycotoxins.

Source: 

Single cell protein can be produced on a number of different substrates, often this is done to reduce the Biological Oxidation Demand of the effluent streams leaving various type of agricultural processing plants.

Feeding Experiments: 

A wide range of substrates can be used to grow microbial proteins (5)(AGRIS 1998-005657)(Kuhad, 1997). Single cell protein has a good potential for a supplemental protein source for feeding livestock (K)(CAB D277040)(Giec, 1988). Various materials can be used as a substrate for producing single cell protein (whey, orange peel residue, sweet orange residue, sugarcane bagasse, paper mill waste, rice husks, wheat straw residue, cassava waste, sugar beet pulp, coconut waste, yam waste, banana pulp, mango waste, grape waste, sweet potato, (A)(CAB N215145)(Vaccarino, 1989); (B)(CAB M550935) (Swaminathan, 1989);(G)(CAB M457080)(Bajpai, 1988); (D)(CAB D319281)(Mathur, 1988); (E)(CAB M507533)(Nwabueze, 1987); (F)(CAB M507592)(El-Shawarby, 1987), (H)(CAB M470931)(Khaled, 1985); (I)(CAB N175836)(Pandey, 1988), (J)(CAB N175844)(Aderiye, 1988), (N)(CAB M389417)(Aker, 1987), (U)(CAB N918111)(Kahlon, 1986), (V)(CAB M693710)(Manilal, 1991), (W)(CAB M694368)(Malathi, 1989), (X)(CAB M681401)(Kuzmanova, 1990), (Y)(CAB D455606)(Zayed, 1991), (AA)(CAB M625510)(El-Refai, 1990), (AC)(CAB N274192)(Bugarski, 1988), (AD)(CAB N266858)(Guo, 1989), (AE)(CAB N252423)(Rashad, 1990), (AH)(CAB 940311026)(Rodriguez, 1993), (AK)(CAB 971300120)(Yulinery, 1995). 

Substrates like bananas have been shown to be excellent substrates that can be used to produce single cell protein. Bananas contain 0.95 % CP, but when subjected to microbial (Aspergillus nigis or Aspergillus foetidus) fermentation the CP level increased to 21.5 %, and up to 20 % could be used in broiler diets (2)(AGRIS 82-803011) (Castillo, 1981). Some microorganisms may produce mycotoxins (L)(CAB M438973)(Sawsan, 1986). Single cell protein seems to be utilized better by ruminant animals. Feeding single cell protein to calves didn. t affect rate of gain, feed or dressing percentage (P)(CAB N935776)(Alwash, 1985). Up to 20 % of single cell protein in the diet had no detrimental affect on performance in calves (AB)(CAB N272009)(Desai, 1988). Similar performance was observed when single cell protein was fed at 0, 5, 10, 15 % levels to lambs (8)(AGRIS 87-032495)(Rammo, 1985). Pulpmill single cell protein was demonstrated to be a viable supplemental protein source for sheep (M)(CAB N035279)(Atil, 1987). It was found that up to 75 % of the total dietary protein can be provided by single cell protein while maintaining normal performance in lambs (6)(AGRIS 89-120973)(Mohammed, 1986). 

Single cell protein was a suitable supplemental protein source for lactating dairy goats (Q)(CAB N910498)(Mudgal, 1986).Milk production and milk production efficiency was increased when single cell protein replaced groundnut meal in lactating goat diets (10)(AGRIS 87-023672)(Mudgal, 1986). Similar performance occurred when single cell protein was fed to layers (AF)(CAB N243009)(Yoshda, 1988). When single cell protein was fed to layers no depression in egg production was observed and the nucleic acid content in tissues and eggs were not affected (9)(AGRIS 87-032359)(Al-Ani, 1985). Layers performance was optimized when single cell protein was fed at 2.5 % of dry matter or 10 % of dietary protein (AG)(CAB N228220)(Ar`kov, 1988). Single cell protein was fed (0, 5, 10, 15 %) levels to poultry and best growth occurred at the 5 and 10 % levels (Z)(CAB N327164)(Al-Shadeedl, 1988). As the dietary level of single cell protein increases in broiler diets the gain, feed conversion, and feed intake decreased (O)(CAB N928109)(Jassim, 1986), (AM)(CAB 20001409666)(Pirmohammadi, 1999). 

Single cell protein was found to be able to replace up to 55 % of the fish meal and soybean meal in swine diets, while still maintaining satisfactory performance (AD)(CAB N266858)(Guo, 1989). Single cell protein (yeast) was found to normal growth in rats, but inferior to casein (1)(AGRIS 82-806782)(Natividad, 1981). Single cell protein was fed to rats at 0, 10, 20 and 30 % levels and was not found to depress growth, feed intake or hematological values (11)(AGRIS 96-103632)(Al-Awadhi, 1995). It was found in mink feeding trials that up to 15 % single cell protein could be included, which was in part do to its lower energy content (3)(AGRIS 82-726869) (Kiiskinen, 1980). Single cell protein was found to be able to replace up to 40 % of fish meal in tilapia diets without affecting performance (C)(CAB N202566)(Davies, 1988). Trout fed single cell protein showed reduced gains (AL)(CAB 971404074)(Perera, 1995). When single cell protein was included in prawn diets there was an increase in gains and feed conversion (AJ)(CAB 971410654)(Manju, 1997). Increase levels of single cell protein resulted in increased uric acid in serum and urine, because of the nucleic acid content (4)(AGRIS 81-602960)(Kamel, 1979).

Nutrient Characteristics: