Evaluation of nutritional value of microbial protein produced with methanol using Methylophilus methylotrophus bacteria

Microbial protein is used in animal and poultry feed. This protein is produced using microorganisms and different carbon sources such as methanol and methane. In this study, Methylophilus methylotrophus bacteria were cultivated in erlen and fermentor using methanol as a carbon source. The specific growth rate of bacteria was 0.0312 h-1 in erlen and 0.0047 h-1 in fermenter. After cultivation, the biomass was separated at optical density of 3.8 using a centrifuge at 7000 rpm, and qualitative and quantitative tests of microbial protein were performed on pellet. Amino acid profile, fatty acid profile, nitrogen content and crude protein were determined using high performance liquid chromatography, gas chromatography and Kjeldahl method, respectively. The results show that the amount of crude protein was 73.5%. The amount of ash was 29.8% and the total of essential to non-essential amino acids (including lysine, histidine, arginine, valine, leucine, isoleucine, phenylalanine, methionine and threonine) was 37.3% for the produced product. The amount of two non-essential amino acids, cysteine and tyrosine, was higher than the FAO standard and was 2.38% and 3.21%, respectively. The ratio of palmitic acid to the total fat of the product is 24.6% (w/w) and the ratio of linoleic acid and linolenic acid as unsaturated fatty acids is 9.2 and 2.3% (w/w) to the total fat of the product, respectively. The results obtained from this research showed that the product with a protein content of 73.5% seems an appropriate candidate for animal feed.