著者

浦上 貞治 寺尾 巌 永井 一郎

出版者

公益社団法人日本生物工学会

雑誌

醗酵工学会誌 : hakkokogaku kaishi (ISSN:03856151)

巻号頁・発行日

vol.64, no.2, pp.99-114, 1986-03-25

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Production of single cell protein (SCP) by methanol-using bacteria was studied. A large number of methanol-using bacteria were isolated from a wide variety of natural sources in Japan. Strain BNK-84 was selected for its growth rate, growth temperature, cell yield, content of crude protein, and content of amino acids, and was identified as Methylobacillus glycogenes (Yordy and Weaver) emend. Urakami and Komagata 1986.Continuous cultures of this strain were done, and the feasibility of SCP production from methanol was studied. Optimum cultural condition were 38℃, pH 6.5-7.0,and a dilution rate of 0.2-0.6h^<-1>. Optimum dissolved oxygen (DO) was 1.5〜10ppm and optimum CO_2 partial pressure (PCO_2) was below 0.14atm. DO-limiting continous cultures were not suitable for the production of SCP because point of the cell yield. Methanol-limiting cultures showed the maximum specific growth rate, 0.60h^<-1>;the cell yield, 45 wt%;the content of crude protein, 86 wt%;the content of amino acids, 70 wt%;and the maximum content of nucleic acids, 20 wt%.For the commercial production of SCP, the continuous cultures with supernatant recycled, with high concentration of cells, and with long-term were studied. The continuous cultures with recycled supernatant were stable. At the feed methanol concentration of 16 wt%, the cell concentration was approximately 6 wt% and cell productivity reached approximately 15 g・l^<-1>・h^<-1>. Long-term continuous cultures (two hundred consecutive days) were stable with respect to the cell yield, the cell composition, and the stability of strain.Mitsubishi Gas Chemical Company (MGC) constructed a pilot plant, equiped with an air-lift fermentor with a nominal volume of 20 m_3,in 1974. Process engineering was done based on the data obtained from this pilot plant for the purpose of scale-up to a further commercial plant. Pilot plant operation was similar to the operation of a small jar fermentor. MGC developed sufficient know-how for the construction and operation of a commercial plant from the pilot plant operation.When SCP is used as the source of animal feed protein, two factors are most important, safety and nutritional value. The pathogenicity of strain BNK-84 was tested in laboratory animals, and it was confirmed to be nonpathogenic. The chemical composition of SCP indicated a high nutritional potential, and the amino acid composition was almost comparable with that of fish meal. Feeding trials of SCP using laying hens, broilers, and pigs were done in various institutes. The nutritional value of SCP was similar to that of soybeans.