Exploring the use of hexadecane by Yarrowia lipolytica: Effect of dissolved oxygen and medium supplementation.

This work aimed to evaluate the effect of medium composition and volumetric oxygen transfer coefficient (kLa) on Y. lipolytica growth and production of microbial lipids and enzymes from hexadecane. In the stirred tank bioreactor, increasing kLa from 11 h-1 to 132 h-1 improved the hexadecane assimilation rate, biomass concentration, and lipids synthesis (0.90 g·L-1). A cost-effective hexadecane-based medium supplemented with corn steep liquor and a low amount of ammonium sulfate boosted lipids production up to 2.1 g·L-1, composed of palmitic, palmitoleic, oleic, and linoleic acids. The unsaturated/saturated fraction was dependent on the C/N ratio. Lipids of Y. lipolytica CBS 2075 are promising feedstock for animal feed, food additives, or the biodiesel industry. Simultaneous synthesis of extracellular lipase and protease from hexadecane was observed, which is a new feature that was not previously reported. The highest enzyme activity was obtained at the highest C/N ratio conditions. These results open new perspectives on the application of Y. lipolytica-based cultures for the biotransformation of hexadecane-polluted streams into valuable compounds, fulfilling an interesting strategy towards the circular economy concept.

Clinical and biochemical short-term effects of hyperbaric oxygen therapy on SARS-Cov-2+ hospitalized patients with hypoxemic respiratory failure.

BACKGROUND: Hyperbaric oxygen therapy (HBOT) has been proposed to address COVID-19- associated respiratory failure. However, its biochemical effects are poorly known. METHOD: 50 patients with hypoxemic COVID-19 pneumonia were divided into C group (standard care) and H group (standard care plus HBOT). Blood was obtained at t = 0 and t = 5 days. Oxygen saturation (O2 Sat) was followed up. White blood cell (WC) count, lymphocytes (L) and platelets (P) and serum analysis (glucose, urea, creatinine, sodium, potassium, ferritin, D dimer, LDH and CRP) were carried out. Plasma levels of sVCAM, sICAM, sPselectin, SAA and MPO, and of cytokines (IL-1ß, IL-1RA, IL-6, TNFα, IFNα, IFNγ, IL-15, VEGF, MIP1α, IL-12p70, IL-2 and IP-10) were measured by multiplex assays. Angiotensin Converting Enzyme 2 (ACE-2) levels were determined by ELISA. RESULTS: The average basal O2 Sat was 85 ± 3%. The days needed to reach O2 Sat >90% were: H: 3 ± 1 and C: 5 ± 1 (P < 0,01). At term, H increased WC, L and P counts (all, H vs C: P < 0,01). Also, H diminished D dimer levels (H vs C, P < 0,001) and LDH concentration (H vs C, P < 0.01]. At term, H showed lower levels of sVCAM, sPselectin and SAA than C with respect to basal values (H vs C: ΔsVCAM: P < 0,01; ΔsPselectin: P < 0,05; ΔSAA: P < 0,01). Similarly, H showed diminished levels of TNFα (ΔTNFα: P < 0,05) and increased levels of IL-1RA and VEGF than C respect to basal values (H vs C: ΔIL-1RA and ΔVEGF: P < 0,05). CONCLUSION: Patients underwent HBOT improved O2 Sat with lower levels of severity markers (WC and platelets count, D dimer, LDH, SAA). Moreover, HBOT reduced proinflammatory agents (sVCAM, sPselectin, TNFα) and increased anti-inflammatory and pro-angiogenic ones (IL-1RA and VEGF).

Bio-oil production for biodiesel industry by Yarrowia lipolytica from volatile fatty acids in two-stage batch culture.

Microbial lipids-derived biodiesel is garnering much attention owing to its potential to substitute diesel fuel. In this study, lipid accumulation by Yarrowia lipolytica from volatile fatty acids (VFAs) was studied in a lab-scale stirred tank bioreactor. In batch cultures, Y. lipolytica NCYC 2904 was able to grow in 18 g·L-1 of VFAs (acetate, propionate, and butyrate), and the addition of a co-substrate (glucose) led to a fivefold improvement in lipid concentration. Furthermore, the two-stage batch culture (growth phase in glucose (1st stage) followed by a lipogenic phase in VFAs (2nd stage)) was the best strategy to obtain the highest lipid content in the cells (37%, w/w), with aeration conditions that kept dissolved oxygen concentration between 40% and 50% of saturation during the lipogenic phase. The estimated fuel properties of biodiesel produced from Y. lipolytica NCYC 2904 lipids are comparable with those of the biodiesel produced from vegetable oils and are in accordance with the international standards (EN 14214 and ASTM D6751). The cultivation strategies herein devised enable a sustainable, eco-friendly, and economical production of microbial lipids, based on feedstocks such as VFAs that can be derived from the acidogenic fermentation of organic wastes. KEY POINTS: • Addition of glucose to VFAs enhances lipids in Y. lipolytica in batch cultures • Two-stage batch culture - growth in glucose followed by VFAs pulse - rises lipids • Dissolved oxygen of 40-50% of saturation is crucial at the lipogenic phase.