Arachidonic acid production by Mortierella alpina with growth-coupled lipid synthesis

The fungus Mortierella alpina LPM 301, a producer of arachidonic acid (ARA), was found to possess a unique property of a growth-coupled lipid synthesis. An increase in specific growth rate (μ) from 0.03 to 0.05 h⁻¹ resulted in a two-fold increase in the specific rate of lipid synthesis (milligram lipid (gram per lipid-free biomass) per hour). Under batch cultivation in glucose-containing media with urea or potassium nitrate as nitrogen sources, the ARA content was 46.0 and 60.4% of lipid; 16.4 and 18.8% of dry biomass; and 4.2 and 4.5 g l⁻¹, respectively. Under continuous cultivation of the strain, the productivity of ARA synthesis was 16.2 and 19.2 mg l⁻¹ h⁻¹ at μ=0.05 and 0.03 h⁻¹, respectively.     

Application of mass and energy balance regularities in fermentation. Reprinted from Biotechnology and Bioengineering, Vol. XX, No. 10, Pages 1595-1621 (1978)

Material and energy balances for fermentation processes are developed based on the facts that the heat of reaction per electron transferred to oxygen for a wide variety of organic molecules, the number of available electrons per carbon atom in biomass, and the weight fraction carbon in biomass are relatively constant. Mass-energy balance equations are developed which relate the biomass energetic yield coefficient to sets of variables which may be determined experimentally. Organic substrate consumption, biomass production, oxygen consumption, carbon dioxide production, heat evolution, and nitrogen consumption are considered as measured variables. Application of the balances using direct and indirect methods of yield coefficient estimation is illustrated using experimental results from the literature. Product formation is included in the balance equations and the effect of product formation on biomass yield estimates is examined. Application of mass-energy balances in the optimal operation of continuous single-cell protein production facilities is examined, and the variation of optimal operating conditions with changes in yield are illustrated for methanol as organic substrate.     

Bacterial degradation of EDTA

Degradation of EDTA (ethylenediaminetetraacetic acid) or metal-EDTA complexes by cell suspensions of the bacterial strain DSM 9103 was studied. The activity of EDTA degradation was the highest in the phase of active cell growth and decreased considerably in the stationary phase, after substrate depletion in the medium. Exponential-phase cells were incubated in HEPES buffer (pH 7.0) with 1 mM of uncomplexed EDTA or EDTA complexes with Mg2+, Ca2+, Mn2+, Pb2+, Co2+, Cd2+, Zn2+, Cu2+, or Fe3+. The metal-EDTA complexes (Me-EDTA) studied could be divided into three groups according to their degradability. EDTA complexes with stability constants K below 10(16) (lg K < 16), such as Mg-EDTA, Ca-EDTA, and Mn-EDTA, as well as uncomplexed EDTA, were degraded by the cell suspensions at a constant rate to completion within 5-10 h of incubation. Me-EDTA complexes with lg K above 16 (Zn-EDTA, Co-EDTA, Pb-EDTA, and Cu-EDTA) were not completely degraded during a 24-hour incubation, which was possibly due to the toxic effect of the metal ions released. No degradation of Cd-EDTA or Fe(III)-EDTA by cell suspensions of strain DSM 9103 was observed under the conditions studied.     

Efficiency of lipid synthesis by yeasts

The efficiency of lipid synthesis by ethanol-grown yeasts is characterized using the coefficient of the lipid energetic yield (eta(1)). This coefficient is defined as the fraction of energy in an organic substrate that is converted to lipids. The advantages of eta(1) compared with the "fat coefficient" (F(s)) as well as the biomass energetic yield (eta) compared with Y(s) are discussed.     

Growth-coupled lipid synthesis in Mortierella alpina LPM 301, a producer of arachidonic acid

Mortierella alpina LPM 301, a producer of arachidonic acid (ARA), was found to possess a unique property of intense lipid synthesis in the period of active mycelium growth. Under batch cultivation of this strain in glucose-containing media with potassium nitrate or urea, the bulk of lipids (28-35% of dry biomass) was produced at the end of the exponential growth phase and remained almost unaltered in the stationary phase. The ARA content of lipids comprised 42-50% at the beginning of the stationary phase and increased continuously after glucose depletion in the medium due to the turnover of intracellular fatty acids; by the end of fermentation (189-210 h), the amount of ARA reached 46-60% of the total fatty acids (16-19% of dry mycelium). Plausible regulatory mechanisms of the growth-coupled lipid synthesis in microorganisms are discussed.     

Effect of lipids from Mortierella hygrophila on plant resistance to phytopathogens

A mixture of fatty acid ethyl esters containing arachidonic acid (ARA) at 30% was isolated from Mortierella hygrophila and applied for a foliar treatment of plants. Field experiments revealed that the lipid preparation used at 0.3–0.5 mg per 100 m² of sown area decreased the development of late blight, common scrab, and rhizoctonoise of potato tubers, cercosporose of sugar beet, and powdery mildew of vine plants by 35–70% as compared to the untreated plants and resulted in a significant increase in the yield.