Proximate composition and amino acid profile of rice husk biodegraded with Pleurotus ostreatusfor different periods
Native rice husk (NRH) was fermented with Pleurotus ostreatus for 7, 14 and 21 days to improve the nutritional values. The proximate composition and amino acid profiles were determined. The results showed that crude fibre (CF), nitrogen free extract (NFE), acid detergent fibre (ADF), and neutral detergent fibre (NDF) were significantly higher (p<0.05) in the NRH (with values 13.37%,42.93%, 17.45% and13.42%, respectively) while corresponding lowest values of 12.14%, 34.26%, 12.27% and 12.41% were obtained in the 14 days samples. Crude protein (CP) was significantly highest (p<0.05) in the 7 days fermentation (12.37%) but lowest in the 21 days (7.94%). The nitrogen free extract (NFE) values were similar and higher (p<0.05) in the NRH (control), 7 and 21 days fermentation that is 42.93%, 40.37% and 39.53%, respectively. The calculated metabolizable energy (ME) was similar and higher (p<0.05) for the fermented native rice husk at 7, 14 and 21 days that is 2289.19, 2308.77 and 2328.59 kcal/kg, respectively. Dry matter (DM), ash, calcium and phosphorous values were not influenced (p<0.05) by the fungi treatment of the NRH. Essential amino acids (EAA) values viz; lysine (4.94 g/100g), valine (7.34 g/100g), threonine (4.81 g/100g), isoleucine (4.83 g/100g) and phenylalanine (5.59 g/100g) were higher (p<0.05) in the 14 days fermentation with p. ostreatus while others that are non-essential amino acids (NEAA) in this group include alanine (7.06 g/100g) and tyrosine (4.12 g/100g). Glycine (6.02 g/100g), serine (5.18 g/100g), proline (4.85 g/100g), leucine (7.44 g/100g), glutamate (14.54 g/100g) and arginine (8.51 g/100g) values were higher (p<0.05) in the 21 days while aspartate (8.70 g/100g), histidine (2.37 g/100g), methionine (2.69 g/100g), tyrosine (4.20 g/100g) and cystine (2.09 g/100g) were higher (p<0.05) in the 7 days treatment. All the amino acids with the exception of glycine, alanine and aspartate had lowest (p<0.05) values recorded in the native rice husk. The total amino acids (TAA), total essential amino acids (TEAA), total non-essential amino acids (TNEAA) were all significantly higher in the 7 days fermentation (95.43, 45.01 and 50.42, respectively) and the lowest values in the NRH. Percent EAA followed the same trend while %NEAA was highest in the NRH. Fermentation of native rice husk for 7 days improved its nutritive value and consequently increased its usage as a component of livestock feed.
Key words: Native Rice Husk, Fermentation, Proximate Composition, Amino Acids