Biology subjects

Vieira-Lara, M. A.

Publications and source records attributed to Vieira-Lara, M. A..

4 recordsLinked to original sources

bioRxiv2024

Specific growth rates and growth stoichiometries of Saccharomycotina yeasts on ethanol as sole carbon and energy substrate

Emerging low-emission production technologies make ethanol an interesting substrate for yeast biotechnology, but information on growth rates and biomass yields of yeasts on ethanol is scarce. Strains of 52 Saccharomycotina yeasts were screened for growth on ethanol. The 21 fastest strains, among which representatives of the Phaffomycetales order were overrepresented, showed specific growth rates in ethanol-grown shake-flask cultures between 0.12 and 0.46 h-1. Seven strains were studied in aerobic, ethanol-limited chemostats (dilution rate 0.10 h-1). Saccharomyces cerevisiae and Kluyveromyces lactis, whose genomes do not encode Complex-I-type NADH dehydrogenases, showed biomass yields of 0.59 and 0.56 gbiomass g -1, respectively. Different biomass yields were observed among species whose genomes do harbour Complex-I genes: Phaffomyces thermotolerans (0.58 g g-1), Pichia ethanolica (0.59 g g-1), Saturnispora dispora (0.66 g g-1), Ogataea parapolymorpha (0.67 g g-1), and Cyberlindnera jadinii (0.73 g g-1). The biomass yield of C. jadinii, which also showed the highest biomass protein content of these yeasts, corresponded to 88% of the theoretical maximum achieved when growth is limited by assimilation rather than by energy availability. This study indicates that energy coupling of mitochondrial respiration and its regulation are key factors for selecting and improving yeast strains for ethanol-based processes.

microbiology↗

bioRxiv2024

Quantitative physiology and biomass composition of Cyberlindnera jadinii in ethanol-grown cultures

BackgroundElimination of greenhouse gas emissions in industrial biotechnology requires replacement of carbohydrates by alternative carbon substrates, produced from CO2 and waste streams. Ethanol is already industrially produced from agricultural residues and waste gas and is miscible with water, self-sterilising and energy-dense. The yeast C. jadinii can grow on ethanol and has a history in the production of single-cell protein (SCP) for feed and food applications. To address a knowledge gap in quantitative physiology of C. jadinii during growth on ethanol, this study investigates growth kinetics, growth energetics, nutritional requirements, and biomass composition of C. jadinii strains in batch, chemostat and fed-batch cultures. ResultsIn aerobic, ethanol-limited chemostat cultures, C. jadinii CBS 621 exhibited a maximum biomass yield on ethanol (Yx/smax) of 0.83 gbiomass (gethanol)-1 and an estimated maintenance requirement for ATP (mATP) of 2.7 mmol{middle dot}(gbiomass)-1{middle dot}h-1. Even at specific growth rates below 0.05 h-1, a stable protein content of approximately 0.54 gprotein{middle dot}(gbiomass)-1 was observed. At low specific growth rates, up to 17% of the proteome consisted of alcohol dehydrogenase proteins, followed by aldehyde dehydrogenases and acetyl-CoA synthetase. Of 13 C. jadinii strains evaluated, 11 displayed fast growth on ethanol (max > 0.4 h-1) in mineral medium without vitamins, and CBS 621 was found to be a thiamine auxotroph. The prototrophic strain C. jadinii CBS 5947 was grown on an inorganic salts medium in fed-batch cultures (10-L scale) fed with pure ethanol. Biomass concentrations in these cultures increased up to 100 gbiomass{middle dot}(kgbroth)-1, with a biomass yield of 0.65 gbiomass{middle dot}(gethanol)-1. Model-based simulation, based on quantitative parameters determined in chemostat cultures, adequately predicted biomass production. A different protein content of chemostat- and fed-batch-grown biomass (54% and 42%, respectively) may reflect the more dynamic conditions in fed-batch cultures. ConclusionsAnalysis of ethanol-grown batch, chemostat and fed-batch cultures provided a quantitative physiology baseline for fundamental and applied research on C. jadinii. Its high maximum growth rate, high energetic efficiency of ethanol dissimilation, simple nutritional requirements and high protein content, make C. jadinii a highly interesting platform for production of SCP and other products from ethanol.

microbiology↗

bioRxiv2023

Age and diet modulate the insulin-sensitizing effects of exercise: a tracer-based oral glucose tolerance test

Diet modulates the development of insulin resistance during aging. This includes tissue-specific alterations in insulin signaling and mitochondrial function, which ultimately affect glucose homeostasis. Exercise stimulates glucose clearance, mitochondrial lipid oxidation and enhances insulin sensitivity. It is not well known how exercise interacts with age and diet in the development of insulin resistance. To investigate this, oral glucose tolerance tests (OGTT) with a tracer were conducted in mice ranging from 4 to 21 months of age, fed a low- (LFD) or high-fat diet (HFD), with or without life-long voluntary access to a running wheel (RW). We developed a computational model to derive glucose fluxes, which were commensurate with independent values from steady-state tracer infusions. Both insulin sensitivity indices derived for peripheral tissues and liver (IS-P and IS-L, respectively) were steeply decreased by aging and a HFD. This preceded the age-dependent decline in the mitochondrial capacity to oxidize lipids. In LFD young animals, RW access enhanced the IS-P concomitantly with the muscle {beta}-oxidation capacity. Surprisingly, RW access completely prevented the age-dependent IS-L decrease, but only in LFD animals. This study indicates, therefore, that endurance exercise can improve the age-dependent decline in organ-specific IS mostly in the context of a healthy diet.

physiology↗

bioRxiv2021

Age-related susceptibility to insulin resistance is due to a combination of CPT1B decline and lipid overload

BACKGROUNDAdvanced age increases the susceptibility to diet-induced insulin resistance (IR). A key driver of this phenomenon is lipid accumulation in the skeletal muscle. It is debated, however, whether this is due to dietary lipid overload or decline of mitochondrial function. To address the interplay of diet and age in the flexibility of muscle lipid and glucose handling, we put young and aged mice on a low- or high-fat diet (HFD). RESULTSAs expected, aged mice were more susceptible to IR when given a HFD than young mice. The HFD induced intramuscular lipid accumulation specifically in aged mice, including C18:0-containing ceramides and diacylglycerols. This was reflected by the mitochondrial {beta}-oxidation capacity, which was upregulated by the HFD in young, but not in old mice. Conspicuously, most {beta}-oxidation proteins were upregulated by the HFD in both groups, but carnitine palmitoyltransferase 1B (CPT1B) declined in aged animals. Computational modelling traced the flux control mostly to CPT1B, suggesting a CPT1B-driven loss of flexibility to the HFD with age. Finally, in old animals glycolytic protein levels were reduced and less flexible to the diet. CONCLUSIONWe conclude that intramuscular lipid accumulation and decreased insulin sensitivity are not due to age-related mitochondrial dysfunction or nutritional overload alone, but rather to their interaction. Moreover, we identify CPT1B as a potential target to counteract age-dependent intramuscular lipid accumulation and thereby IR.

biochemistry↗