Achieving a high-density oleaginous yeast culture: Comparison of four processing strategies using Metschnikowia pulcherrima

Microbial lipids have the potential to displace terrestrial oils for fuel, value chemical, and food production, curbing the growth in tropical oil plantations and helping to reduce deforestation. However, commercialization remains elusive partly due to the lack of suitably robust organisms and their low lipid productivity. Extremely high cell densities in oleaginous cultures are needed to increase reaction rates, reduce reactor volume, and facilitate downstream processing. In this investigation, the oleaginous yeast Metschnikowia pulcherrima, a known antimicrobial producer, was cultured using four different processing strategies to achieve high cell densities and gain suitable lipid productivity. In batch mode, the yeast demonstrated lipid contents more than 40% (w/w) under high osmotic pressure. In fed-batch mode, however, high-lipid titers were prevented through inhibition above 70.0 g L⁻¹ yeast biomass. Highly promising were a semi-continuous and continuous mode with cell recycle where cell densities of up to 122.6 g L⁻¹ and maximum lipid production rates of 0.37 g L⁻¹ h⁻¹ (daily average), a nearly two-fold increase from the batch, were achieved. The findings demonstrate the importance of considering multiple fermentation modes to achieve high-density oleaginous yeast cultures generally and indicate the limitations of processing these organisms under the extreme conditions necessary for economic lipid production.     

Polymorphism of genes involved in anti-tubular basement membrane disease in rats

Inbred strains of rats differ widely in their susceptibility to interstitial nephritis induced by rabbit renal tubular basement membrane (TBM) preparations. We now report that susceptibility is determined in part by an RTI-linked gene for effector cell responsiveness producing interstitial lesions. Furthermore we also obtained evidence that the gene determining expression of the target TBM antigen is linked to the gene for albinism on the first linkage group. When non-susceptible rats lacking the TBM antigen but having the gene for cellular responsiveness were mated with non-susceptible rats which had the TBM antigen but lacked the gene for cellular responsiveness, the F₁ hybrids were susceptible to the induction of interstitial nephritis. Although strains varied widely in the amount of anti-TBM antibody (αTBM-Ab) they produced, this variation does not appear to be controlled by RTI-linked genes, nor does the isotype or amount of antibody appear to be related to the susceptibility to infiltrating cellular lesions.     

Novel structure of a high molecular weight FK506 binding protein fromArabidopsis thaliana

We have isolated clones of an Arabidopsis gene (ROF1, forrotamaseFKBP) encoding a high molecular weight member of the FK506 binding protein (FKBP) family. The deduced amino acid sequence of ROF1 predicts a 551-amino acid, 62 kDa polypeptide which is 44% identical to human FKBP59 — a 59 kDa FKBP which binds to the 90 kDa heat shock protein and is associated with inactive steroid hormone receptors. ROF1 contains three FKBP12-like domains in the N-terminal portion of the protein (in contrast to two domains in mammalian FKBP59), an internal repeat structure associated with protein-protein interactions (tetratricopeptide repeats), and a putative calmodulin binding domain near the C-terminal region of the protein. No sequences associated with protein translocation out of the cytosol were found in ROF1.ROF1 mRNA was found at equivalent low levels in light-grown roots, stems, and flowers and at slightly higher levels in leaves. The abundance ofROF1 mRNA increased several-fold under stress conditions such as wounding or exposure to elevated NaCl levels.The nucleotide sequences in this paper have been submitted to the GenBank/EMBL Data bank with accession numbers U49453 and U57838     

DNA topoisomerase II mutations and resistance to anti-tumor drugs

Mutations in DNA topoisomerase II are often correlated with drug-resistance in tumor cell lines. Studies of topoisomerase II-mediated drug-resistance in various model systems, as well as the sequencing of such mutations from drug-resistant tumors, have shed light on the functional domains of topoisomerase II, on how it interacts with inhibitors, and on the different mechanisms by which cells avoid the toxic effects of many clinically important anti-tumor drugs.     

Determination of hopanoid levels in bacteria using high-performance liquid chromatography

A reverse-phase HPLC method to detect and quantify levels of hopanoids in bacteria has been developed. Chromophores have been introduced by derivatization and the levels of the C35 hopanoids and their conjugates can be measured in bacterial lipid extracts down to picomole levels. Some structural variations of the complex lipids were detected after derivatization and were easily purified using the same HPLC system. Zymomonas mobilis and Rhodospirillum rubrum extracts were examined using this system and different structural examples of the lipids were detected. The relative levels of the different triterpenes were very dependent on the growth conditions.