- Publikační typ
- abstrakt z konference MeSH
Microalgae accumulate bioavailable selenium-containing amino acids (Se-AAs), and these are useful as a food supplement. While this accumulation has been studied in phototrophic algal cultures, little data exists for heterotrophic cultures. We have determined the Se-AAs content, selenium/sulfur (Se/S) substitution rates, and overall Se accumulation balance in photo- and heterotrophic Chlorella cultures. Laboratory trials revealed that heterotrophic cultures tolerate Se doses ∼8-fold higher compared to phototrophic cultures, resulting in a ∼2-3-fold higher Se-AAs content. In large-scale experiments, both cultivation regimes provided comparable Se-AAs content. Outdoor phototrophic cultures accumulated up to 400 μg g-1 of total Se-AAs and exhibited a high level of Se/S substitution (5-10%) with 30-60% organic/total Se embedded in the biomass. A slightly higher content of Se-AAs and ratio of Se/S substitution was obtained for a heterotrophic culture in pilot-scale fermentors. The data presented here shows that heterotrophic Chlorella cultures provide an alternative for Se-enriched biomass production and provides information on Se-AAs content and speciation in different cultivation regimes.
- MeSH
- aminokyseliny analýza metabolismus MeSH
- biomasa MeSH
- Chlorella klasifikace růst a vývoj metabolismus účinky záření MeSH
- fototrofní procesy MeSH
- heterotrofní procesy MeSH
- mikrořasy chemie růst a vývoj metabolismus účinky záření MeSH
- selen analýza metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
Nitrilases from Aspergillus niger CBS 513.88, A. niger K10, Gibberella moniliformis, Neurospora crassa OR74A, and Penicillium marneffei ATCC 18224 were expressed in Escherichia coli BL21-Gold (DE3) after IPTG induction. N. crassa nitrilase exhibited the highest yield of 69,000 U L(-1) culture. Co-expression of chaperones (GroEL/ES in G. moniliformis and P. marneffei; GroEL/ES and trigger factor in N. crassa and A. niger CBS 513.88) enhanced the enzyme solubility. Specific activities of strains expressing the former two enzymes increased approximately fourfold upon co-expression of GroEL/ES. The enzyme from G. moniliformis (co-purified with GroEL) preferred benzonitrile as substrate (K(m) of 0.41 mM, V(max) of 9.7 μmol min(-1) mg(-1) protein). The P. marneffei enzyme (unstable in its purified state) exhibited the highest V(max) of 7.3 μmol min(-1) mg(-1) protein in cell-free extract, but also a high K(m) of 15.4 mM, for 4-cyanopyridine. The purified nitrilases from A. niger CBS 513.88 and N. crassa acted preferentially on phenylacetonitrile (K(m) of 3.4 and 2.0 mM, respectively; V(max) of 10.6 and 17.5 μmol min(-1) mg(-1) protein, respectively), and hydrolyzed also (R,S)-mandelonitrile with higher K(m) values. Significant amounts of amides were only formed by the G. moniliformis nitrilase from phenylacetonitrile and 4-cyanopyridine.
- MeSH
- aminohydrolasy chemie genetika izolace a purifikace metabolismus MeSH
- Escherichia coli genetika MeSH
- exprese genu MeSH
- fungální proteiny chemie genetika izolace a purifikace metabolismus MeSH
- houby enzymologie genetika MeSH
- kinetika MeSH
- klonování DNA MeSH
- koncentrace vodíkových iontů MeSH
- molekulární chaperony genetika metabolismus MeSH
- rekombinantní proteiny chemie genetika izolace a purifikace metabolismus MeSH
- stabilita enzymů MeSH
- substrátová specifita MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
