Obligate Methylotrophic Bacteria from Cactus Fruits as Producers of Feed Protein

New methylotrophic bacteria, strains Pita1 and Pita2, were isolated from the tissues of pitahaya fruits (cactus Hylocereus sp.). Phylogenetic analysis revealed that the isolates belonged to the same Methylobacillus species. They obligately utilized only C1-compounds as carbon and energy sources, and showed high growth rates on a mineral medium containing methanol (µmax 0.45 h–1) with an economic coefficient (Y 0.40). Palmitic and palmitoleic acids predominated in the fatty acid composition of the cells. Since the biomass of the studied strains growing on an inexpensive non-food substrate (methanol) had a crude protein content of ~80%, a total amino acid content of ~70%, high levels of essential amino acids, and high digestibility by proteolytic enzymes in vitro (97.3%), these organisms have a potential as feed protein producers.