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[Growth characteristics of haploid and diploid Hansenula polymorpha yeasts on methanol in continuous culture]
Abstract:
The rate of growth and the yield of biomass of a Hunsenula polymorpha homozygous diploid strain ML-3 X ML-3 were nearly identical with those of the parent haploid culture ML-3. The two cultures were eliminated from the fermenter at D = 0.20 to 0.21 h-1. In contrast, a heterozygous diploid strain ML-3 X VKM 1397 could grow at D = 0.23 to 0.25 h-1 and its biomass yield reached 38% while the yields of the haploid and homozygous diploid strains were 35 to 36%. The pH of the medium had the same effect on the three cultures: a change in the pH from 4.0 to 3.5 and then to 3.0 did not influence the yield of biomass; a further pH drop to 2.5 made the cells be eliminated from the fermenter.
Insights
Heterozygous diploid strains of Hunsenula polymorpha exhibit enhanced growth rates and biomass yield compared to homozygous diploid and haploid strains. Optimal pH for biomass yield is between 3.0 and 4.0.
Area of Science:
- Biotechnology
- Microbiology
- Yeast Genetics
Background:
- Hansenula polymorpha is a methylotrophic yeast with industrial applications.
- Diploid strains can offer advantages over haploid strains in certain biotechnological processes.
- Understanding the growth characteristics of different ploidy levels is crucial for optimizing fermentation.
Purpose of the Study:
- To compare the growth rate and biomass yield of haploid, homozygous diploid, and heterozygous diploid strains of Hansenula polymorpha.
- To investigate the effect of dilution rate (D) and pH on the performance of these yeast cultures.
- To determine if diploidization enhances the biotechnological potential of Hansenula polymorpha.
Main Methods:
- Cultivation of haploid, homozygous diploid, and heterozygous diploid Hansenula polymorpha strains in a fermenter.
- Measurement of growth rate and biomass yield under varying dilution rates (D).
- Assessment of biomass yield at different pH levels (4.0, 3.5, 3.0, 2.5).
Main Results:
- Homozygous diploid strains showed growth rates and biomass yields similar to the parent haploid strain (ML-3).
- Heterozygous diploid strains (ML-3 X VKM 1397) demonstrated a higher maximum growth rate (D = 0.23–0.25 h-1) and increased biomass yield (38%) compared to haploid and homozygous diploid strains (35–36%).
- Biomass yield was unaffected by pH changes from 4.0 to 3.0, but a further drop to pH 2.5 led to cell elimination.
Conclusions:
- Heterozygous diploidization can significantly improve the fermentation performance of Hansenula polymorpha.
- The optimal pH range for biomass production in these strains is between 3.0 and 4.0.
- These findings suggest that heterozygous diploid strains are more suitable for industrial applications requiring high biomass yield.