To investigate the effects of lactate on cell growth and antibody production, a new method of maintaining the lactate concentration constant in a fed-batch culture is described. When the pH was initially adjusted by sodium hydroxide, the specific growth rate decreased and specific death rate increased with an increase of lactate concentration. To investigate whether the inhibition was due to the lactate concentration itself or to the osmotic pressure, the effect of the osmotic pressure adjusted by sodium chloride was compared with that of sodium lactate. When the osmotic pressure was adjusted to same condition as that of sodium lactate using sodium chloride, the specific growth data showed the same degree of growth inhibition. It was thus evident that the inhibition to cell growth was mainly due to osmotic pressure while lactate production from glucose was found to be inhibited by the lactate itself compared with sodium chloride. The specific antibody production rate had a maximum value within a certain range of lactate concentration. Moreover, specific antibody production rate had a unified relationship with the kinetic parameter mu, in spite of the different causes of inhibition by lithium lactate and sodium lactate. A certain "trade-off" relationship between growth and antibody production existed at higher growth rates.

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A filamentous fungus producing significant levels of arachidonic acid (AA, C20:4n-6) was isolated from a freshwater pond sample and assigned to the species Mortierella alliacea. This strain, YN-15, accumulated AA mainly in the form of triglyceride in its mycelia. An optimized culture in 25 L of medium containing 12% glucose and 3% yeast extract yielded 46.1 g/L dry cell weight, 19.5 g/L total fatty acid, and 7.1 g/L AA by 7-d cultivation in a 50-L jar fermenter. Assimilation of soluble starch by YN-15 was notably enhanced by the addition of oleic acid, soybean oil, ammonium sulfate, or potassium phosphate to a starch-based medium. Using starch as a main carbon source in the pre-pilot scale cultivation improved the production of AA by up to 5.0 g/L. Mortierella alliacea strain YN-15 is therefore a promising fungal isolate for industrial production of AA and other polyunsaturated fatty acids.Paper no. J9821 in JAOCS 78, 599-604 (June 2001).

Dihomo-γ-linolenic acid (DGLA)-containing oil (triacylglycerol) was produced by the fungus Mortierella alpina S14, which is a ∆5 desaturase-defective mutant of the arachidonic acid-producing strain 1S-4. Using soy flour as the nitrogen source, S14 produced 8.1 g DGLA/L of culture medium in a 50-L jar fermenter. Shifting the cultivation temperature from 26 to 28°C resulted in reduction of the percentage of DGLA in total fatty acids. Under optimal conditions in a 10-kL industrial fermenter, DGLA production reached 7.0 g/L (percentage of DGLA, 43.9%) at day 12 of cultivation. The other fatty acids were palmitic (18.2%), stearic (7.9%), oleic (7.5%), linoleic (4.4%), γ-linolenic (3.2%), arachidonic (0.4%), and lignoceric (7.7%) acids.