Lipid production by the oleaginous yeast Yarrowia lipolytica using industrial by-products under different culture conditions

BACKGROUND: Microbial lipid production using renewable feedstock shows great promise for the biodiesel industry. RESULTS: In this study, the ability of a lipid-engineered Yarrowia lipolytica strain JMY4086 to produce lipids using molasses and crude glycerol under different oxygenation conditions and at different inoculum densities was evaluated in fed-batch cultures. The greatest lipid content, 31% of CDW, was obtained using a low-density inoculum, a constant agitation rate of 800 rpm, and an oxygenation rate of 1.5 L/min. When the strain was cultured for 450 h in a chemostat containing a nitrogen-limited medium (dilution rate of 0.01 h(−1); 250 g/L crude glycerol), volumetric lipid productivity was 0.43 g/L/h and biomass yield was 60 g CDW/L. The coefficient of lipid yield to glycerol consumption (Y(L/gly)) and the coefficient of lipid yield to biomass yield (Y(L/X)) were equal to 0.1 and 0.4, respectively. CONCLUSIONS: These results indicate that lipids may be produced using renewable feedstock, thus providing a means of decreasing the cost of biodiesel production. Furthermore, using molasses for biomass production and recycling glycerol from the biodiesel industry should allow biolipids to be sustainably produced

Chapter 6: Production and Applications of Polyunsaturated Fatty Acids

Polyunsaturated fatty acids (PUFAs) are key molecules for the control of human as well as animal health. Among the PUFAs, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are vital compounds for infant brain development and other immune regulatory functions. Commercially available omega fatty acids are obtained from fish sources; nowadays fish oils are not preferred due to its unpalatable taste and odors as well as the fact that this resource is declining. Microalgae and other microorganisms based polyunsaturated fatty acids are gaining more attraction because of its fastest growth and lipids content; it is a preferred resource for vegetarians for omega 3/6 oils. Genetically modified organisms such as yeast are utilized for desired fatty acids production commercially. This chapter discusses the importance of polyunsaturated fatty acids for human health, various sources of PUFAs along with its fermentative productions and future perspective

Plant peroxisomal ABC transporters: flexible and unusual

ABC transporters of subfamily D mediate import of substrates for β-oxidation into peroxisomes. Whilst mammals possess three peroxisomal ABCD proteins which homodimerise to form transporters with distinct substrate specificities, Baker’s yeast has a single transporter formed by heterodimerisation, which imports long-chain fatty acyl CoAs. Plants have a single-fused heterodimer transporter that exhibits broad substrate specificity, reflecting the wide range of β-oxidation substrates processed by plants. The fusion appears to have occurred early in the evolution of land plants and was followed by an early duplication event in the monocot lineage. Plant ABCD proteins function in all stages of the life cycle and their physiological roles reflect the ability to transport diverse substrates including saturated and unsaturated fatty acids and aromatic compounds such as precursors of hormones and secondary metabolites. Recent work suggests that transport of CoA substrates involves their cleavage and re-esterification within the peroxisome, thus interaction with appropriate acyl adenylate-activating enzymes potentially provides a mechanism for regulating entry of different substrates into β-oxidation. The mechanism of ABCD transporter targeting is broadly conserved across kingdoms but evidence suggests the regulation of protein turnover differs

Duration of ruptured membranes and vertical transmission of HIV-1: a meta-analysis from 15 prospective cohort studies

Objective: To test the a priori hypothesis that longer duration of ruptured membranes is associated with increased risk of vertical transmission of HIV. Design: The relationship between duration of ruptured membranes and vertical transmission of HIV was evaluated in an individual patient data meta-analysis. Methods: Eligible studies were prospective cohort studies including at least 100 mother-child pairs, from regions where HIV-infected women are counselled not to breastfeed. Analyses were restricted to vaginal deliveries and non-elective Cesarean sections; elective Cesarean section deliveries (those performed before onset of labour and before rupture of membranes) were excluded. Results: The primary analysis included 4721 deliveries with duration of ruptured membranes less than or equal to 24 h. After adjusting for other factors known to be associated with vertical transmission using logistic regression analysis to assess the strength of the relationship, the risk of vertical HIV transmission increased approximately 2% with an increase of 1 h in the duration of ruptured membranes [adjusted odds ratio, 1.02; 95% confidence interval, 1.01-1.04; for each 1 h increment]. There were no significant interactions of duration of ruptured membranes with study cohort or with any of the covariates, except maternal AIDS. Among women diagnosed with AIDS, the estimated probability of transmission increased from 8% to 31% with duration of ruptured membranes of 2 h and 24 h respectively (P < 0.01). Conclusions: These results support the importance of duration of ruptured membranes as a risk factor for vertical transmission of HIV and suggest that a diagnosis of AIDS in the mother at the time of delivery may potentiate the effect of duration of ruptured membranes. (C) 2001 Lippincott Williams & Wilkins