Biochemical conversions by yeast fermentation at high cell densities

In a fermentation process of producing yeast cells wherein at least one yeast is cultured in fermentation means characterized as being free from physical means to remove liquid medium from said aqueous ferment without removing cells, under aqueous aerobic fermentation conditions in an aqueous ferment comprising yeast cells and aqueous liquor employing yeast-assimilable carbon energy substrate, assimilable nitrogen source, water, oxygen, and mineral salts,

• removing aqueous ferment as effluent from said fermenter means, and
• recovering the so-produced yeast cells as a single cell protein product,
• wherein said carbon energy substrate is selected from the group consisting of carbohydrates, alcohols, ketones, aldehydes, acids, and esters, of 1 to 20 carbon atoms per molecule;
• and normal paraffins of 10 to 20 carbon atoms per molecule,
• wherein the improvement comprises:
• employing as said yeast a species selected from the group consisting of Pichia pastoris NRRL Y-11430, Pichia pastoris NRRL Y-11431, and Hansenula polymorpha NRRL Y-11432;
• and
• feeding sufficient said mineral salts to said aqueous ferment at a rate effective to maintain in said aqueous ferment the following elements in at least the designated minimum amounts, per liter of aqueous ferment:
• P 1.9 g, K 1 g, Mg 0.15 g, Ca 0.06 g, S 0.1 g, Fe 6 mg, Zn 2 mg, Cu 0.6 mg, and Mn 0.6 mg,
• thereby maintaining a cell density in said aqueous ferment of about 60 to 160 grams, on a dried basis, per liter of aqueous ferment.

In a continuous process of biochemical conversion wherein a carbon energy substrate is converted to products of fermentation, which comprises culturing at least one yeast under aerobic aqueous fermentation conditions, in aqueous ferment comprising a cellular phase and an aqueous extracellular phase, employing a yeast-assimilable carbon energy substrate, assimilable nitrogen source, water, molecular oxygen, and mineral salts,

• wherein the improvement comprises:
• employing a yeast selected from the group consisting of Pichia pastoris NRRL Y-11430, Pichia pastoris NRRL Y-11431, and Hansenula polymorpha NRRL Y-11432, and
• feeding said mineral salts to said aqueous ferment in an amount sufficient to maintain in said aqueous ferment the following elements in at least the designated amounts per liter of aqueous ferment:
• P 1.9 g, K 1 g, Mg 0.15 g, Ca 0.06 g, S 0.1 g, Fe 6 mg, Zn 2 mg, Cu 0.6 mg, and Mn 0.6 mg, and said carbon energy substrate in amounts required for maximum growth of cells,
• maintaining a yeast cell density in said aqueous ferment of about 60 to 160 grams on a dried basis per liter of said aqueous ferment, and producing at least one product of fermentation.

A fermentation process of producing yeast protein product, which comprises culturing a yeast under aqueous aerobic fermentation conditions, in aqueous ferment comprising yeast cells and aqueous liquor, employing yeast-assimilable carbon energy substrate, assimilable nitrogen source, water, oxygen, and mineral salts comprising a primary salts medium and a trace mineral salts,

• feeding sufficient said mineral salts to said aqueous ferment to maintain the following elements in at least the minimum amount, per liter of aqueous ferment:
• P 1.9 g, K 1 g, Mg 0.15 g, Ca 0.06 g, S 0.1 g, Fe 6 mg, Zn 2 mg, Cu 0.6 mg, and Mn 0.6 mg, thereby maintaining a cell density in said aqueous ferment of about 60 to 160 grams, on a dried basis, per liter of aqueous ferment,
• employing a fermenter characterized as being free from physical means to remove liquid medium from said aqueous ferment without removing cells, and
• recovering the resulting yeast microorganisms,
• wherein said carbon energy substrate is selected from the group consisting of carbohydrates, alcohols, ketones, aldehydes, acids, and esters, of 1 to 20 carbon atoms per molecule;
• and normal paraffins of 10 to 20 carbon atoms per molecule.