Volatile fatty acids as novel building blocks for oil-based chemistry via oleaginous yeast fermentation.

Microbial oils are proposed as a suitable alternative to petroleum-based chemistry in terms of environmental preservation. These oils have traditionally been studied using sugar-based feedstock, which implies high costs, substrate limitation, and high contamination risks. In this sense, low-cost carbon sources such as volatile fatty acids (VFAs) are envisaged as promising building blocks for lipid biosynthesis to produce oil-based bioproducts. VFAs can be generated from a wide variety of organic wastes through anaerobic digestion and further converted into lipids by oleaginous yeasts (OYs) in a fermentation process. These microorganisms can accumulate in the form of lipid bodies, lipids of up to 60% wt/wt of their biomass. In this context, OY is a promising biotechnological tool for biofuel and bioproduct generation using low-cost VFA media as substrates. This review covers recent advances in microbial oil production from VFAs. Production of VFAs via anaerobic digestion processes and the involved metabolic pathways are reviewed. The main challenges as well as recent approaches for lipid overproduction are also discussed.

Assessing the potential of olive mill solid waste as feedstock for methane and volatile fatty acids production via anaerobic bioprocesses.

The extensive production of olive mill solid waste (OMSW) from olive oil industry in the Mediterranean basin claims effective treatments and valorization strategies. This study aims to elucidate the potential of anaerobic digestion (AD) and anaerobic fermentation (AF) to convert pre-treated OMSW into biogas (CH4) and volatile fatty acids (VFA), respectively. The two thermal treatment conditions (65 °C and 180 °C) that are being implemented in the industry that manages the OMSW were tested. Comparing the two treatments aims to demonstrate the influence on the AD process of the degree of solubilization and degradation of the metabolites produced from the same substrate. AD of OMSW treated at low-temperature (65 °C) exhibited similar methane yields (195 ± 8 mL CH4/g volatile solid (VS)) to raw OMSW. AD of the solid phase (SP) after high-temperature treatment with acid addition at 180 °C resulted in methane yields comparable to raw OMSW while the liquid phase (LP) exhibited low methane yields (85 ± 10 mL CH4/g VS). Nevertheless, LP/180 °C exhibited the highest VFA bioconversion at 27.6 %, compared to less than 10 % for SP/180 ºC, SP/65 °C, and raw OMSW. The VFA profile showed notable variations with thermal treatment temperatures. Propionic acid dominated at SP/65 °C, while acetic acid became the primary VFA at 180 °C. Furthermore, significant degradation rates of phenolic compounds and furans were observed during the final day of both anaerobic processes. Overall, these findings suggest that AD is more suitable for raw OMSW, treated at low temperature and SP at high temperature, while AF offers a promising alternative for high-temperature-treated LP.

Mixotrophic cultivation of microalgae-bacteria consortia enhances dark fermentation effluent treatment.

Dark fermentation (DF) is a waste treatment bioprocess which produces biohydrogen and volatile fatty acids (VFAs) such as acetate or butyrate. DF can be coupled with microalgae cultivation, allowing VFA conversion into valuable biomass. Nevertheless, the process is hindered by slow butyrate consumption. In this study, novel artificial microalgae-bacteria consortia were used as a strategy to accelerate butyrate removal. Three microalgal strains with various trophic metabolisms, Chlorella sorokiniana, Euglena gracilis and Ochromonas danica, were cultivated on DF effluent that was either sterile or contained endogenous bacteria. Bacteria did not impact microalgal biomass production of C. sorokiniana or E. gracilis while accelerating butyrate removal rates 2 to 10-fold. O. danica greatly impacted microbial diversity, probably due to its phagotrophic metabolism. These results show that bacteria in organic rich effluents can greatly aid in substrate removal while allowing microalgal growth, inspiring bioprocesses coupling raw fermentation effluents with microalgae biomass production and valorization.

Microbial co-cultures for biochemicals production from lignocellulosic biomass: A review.

Global reliance on fossil oil should shift to cleaner alternatives to get a decarbonized society. One option to achieve this ambitious goal is the use of biochemicals produced from lignocellulosic biomass (LCB). The inherent low biodegradability of LCB and the inhibitory compounds that might be released during pretreatment are two main challenges for LCB valorization. At microbiological level, constraints are mostly linked to the need for axenic cultures and the preference for certain carbon sources (i.e., glucose). To cope with these issues, this review focuses on efficient LCB conversion via the sugar platform as well as an innovative carboxylate platform taking advantage of the co-cultivation of microorganisms. This review discusses novel trends in the use of microbial communities and co-cultures aiming at different bioproducts co-generation in single reactors as well as in sequential bioprocess combination. The outlook and further perspectives of these alternatives have been outlined for future successful development.

Dark fermentation and microalgae cultivation coupled systems: Outlook and challenges.

The implementation of a sustainable bio-based economy is considered a top priority today. There is no doubt about the necessity to produce renewable bioenergy and bio-sourced chemicals to replace fossil-derived compounds. Under this scenario, strong efforts have been devoted to efficiently use organic waste as feedstock for biohydrogen production via dark fermentation. However, the technoeconomic viability of this process needs to be enhanced by the valorization of the residual streams generated. The use of dark fermentation effluents as low-cost carbon source for microalgae cultivation arises as an innovative approach for bioproducts generation (e.g., biodiesel, bioactive compounds, pigments) that maximizes the carbon recovery. In a biorefinery context, after value-added product extraction, the spent microalgae biomass can be further valorised as feedstock for biohydrogen production. This integrated process would play a key role in the transition towards a circular economy. This review covers recent advances in microalgal cultivation on dark fermentation effluents (DFE). BioH2 via dark fermentation processes and the involved metabolic pathways are detailed with a special focus on the main aspects affecting the effluent composition. Interesting traits of microalgae and current approaches to solve the challenges associated to the integration of dark fermentation and microalgae cultivation are also discussed.

Carboxylic acids production via anaerobic fermentation: Microbial communities' responses to stepwise and direct hydraulic retention time decrease.

Carboxylic acids, traditionally produced from fossil fuels, might be generated from renewable biomass resources via anaerobic fermentation. Considering that the microbial activity of this bioprocess is ruled by the imposed hydraulic retention time (HRT), this investigation explored the relationship between process stability and microbial community. Stepwise and direct HRT reduction strategies were assessed in terms of waste bioconversion into volatile fatty acids (VFAs). Microbial community dynamics revealed a microbial specialization along the HRT decrease. The direct implementation of low HRT resulted in drastic microbial fluctuations, leading to process failure at HRT below 6 days. Stepwise strategy for HRT reduction favored microbial adaptation, supporting maximum bioconversions efficiencies (32 % VFACOD/tCODin) at low HRT values (HRT 4 days). Microbial similarity analysis revealed Clostridiales, Lactobacillales and Bacteroidales orders as keystone microorganisms involved in VFAs production, being responsible for protein degradation and propionic acid accumulation.

Tuning microbial community in non-conventional two-stage anaerobic bioprocess for microalgae biomass valorization into targeted bioproducts.

Unspecific microorganisms consortia are normally used in anaerobic biodegradation of solid wastes. However, these consortia can be tuned to optimally obtain determined bioproducts. In this study, high value-added products and biogas were obtained via an innovative two-stage anaerobic bioprocess from microalgae biomass. The anaerobic fermentation (AF) entailed the production of short-chain fatty acids (SCFAs) and subsequently, only the solid spent of AF effluent was valorized for methane production via conventional anaerobic digestion (AD). Applied conditions in AF (25 °C, HRT 8 days) favored Firmicutes predominance (64%) enabling a conversion efficiency of 32.1% g SCFAs-COD/g CODin. Opposite, a wider microbial biodiversity was determined in the AD reactor (35 °C, HRT 20 days), being mainly composed by Firmicutes (28.6%), Euryarchaeota (17.7%) and Proteobacteria (15.3%). AD of the AF-solid spent reached 168.9 mL CH4 /g CODin. Strikingly, operational conditions imposed mediated a microbial specialization that maximized product output.

Insights on the microbial communities developed during the anaerobic fermentation of raw and pretreated microalgae biomass.

Short-chain fatty acids (SCFAs) are considered building blocks for bioproducts in the so-called carboxylate platform. These compounds can be sustainably produced via anaerobic fermentation (AF) of organic substrates, such as microalgae. However, SCFAs bioconversion efficiency is hampered by the hard cell wall of some microalgae. In this study, one thermal and two enzymatic pretreatments (carbohydrases and proteases) were employed to enhance Chlorella vulgaris biomass solubilization prior to AF. Pretreated and non-pretreated microalgae were assessed in continuous stirred tank reactors (CSTRs) for SCFAs production. Aiming to understand microorganisms' roles in AF depending on the employed substrate, not only bioconversion yields into SCFAs were evaluated but microbial communities were thoroughly characterized. Proteins were responsible for the inherent limitation of raw biomass conversion into SCFAs. Indeed, the proteolytic pretreatment resulted in the highest bioconversion (33.4% SCFAs-COD/CODin), displaying a 4-fold enhancement compared with raw biomass. Population dynamics revealed a microbial biodiversity loss along the AF regardless of the applied pretreatment, evidencing that the imposed operational conditions specialized the microbial community. In fact, a reduced abundance in Euryarchaeota phylum explained the low methanogenic activity, implying SCFAs accumulation. The bacterial community developed in the reactors fed with pretreated microalgae exhibited high acidogenic activities, being dominated by Firmicutes and Bacteroidetes. Firmicutes was by far the dominant phylum when using protease (65% relative abundance) while Bacteroidetes was prevailing in the reactor fed with carbohydrase-pretreated microalgae biomass (40% relative abundance). This fact indicated that the applied pretreatment and macromolecule solubilization have a strong effect on microbial distribution and therefore in SCFAs bioconversion yields.

The impact of "faster aspart" on blood glucose control in children and adolescents with type 1 diabetes treated using a sensor-augmented insulin pump.

BACKGROUND AND AIMS: Post-prandial glucose control is essential to achieve metabolic goals in patients with type 1 diabetes mellitus (T1DM). The new "faster aspart" insulin has a pharmacological profile noted for its faster absorption and onset of action, and increased early availability, resulting in improved blood glucose control after meals. The main objective of the study was to analyse the efficacy of "faster aspart" vs. "insulin aspart" in children and adolescents with DM1 on sensor-augmented pump treatment. PATIENTS AND METHODS: Multicentre, longitudinal and prospective analytical trial evaluating the use of faster aspart insulin for three months in children with T1DM with MiniMed640G® sensor-augmented pumps previously treated with aspart insulin. At the beginning and end of the study the following variables were analysed for subsequent comparison: mean sensor glucose, percentage of time in range, hypoglycaemia and hyperglycaemia, area under the curve (AUC) <70 and >180 mg/dL, mean sensor glucose pre- and postprandial in main meals, daily insulin requirements, basal/bolus percentage, and HbA1c. Acute complications, adverse events and satisfaction survey were assessed. RESULTS: The study included 32 patients with a mean of 13.49 ± 2.42 years of age and with T1DM of 7.0 ± 3.67 years of onset. The use of faster aspart was associated with lower time in hyperglycaemia >180 mg/dL (25.8 ± 11.3 vs. 22.4 ± 9.5; p = .011) and >250 mg/dL (5.2±4.9 vs. 4.0 ± 3.6; p = .04), lower AUC >180 mg/dL (10.8 ± 6.5 vs. 9.3 ± 6.1; p = .03), and increased time in range (71.4 ± 10.0 vs. 74.3 ± 9.2; p = .03). No significant changes in hypoglycaemia, HbA1c, insulin requirements, and basal/bolus percentages were detected. Faster aspart was safe and well-evaluated by patients and caregivers. CONCLUSIONS: Faster aspart achieves better glycaemic control by increasing glucose time in range in children and adolescents with T1DM on treatment with sensor-augmented pumps.

VOLATILE FATTY ACIDS FROM ORGANIC WASTES AS NOVEL LOW-COST CARBON SOURCE FOR Yarrowia lipolytica.

Microbial oil biosynthesis is envisaged as a promising technology for sustainable production of chemicals and fuels. Sugar-based substrates are the most typical carbon sources used for this purpose where metabolic pathways and stoichiometry are well known. However, the use of low-cost substrates is crucial for the economic viability of the process. Volatile fatty acids (VFAs) are considered to be a novel low-cost carbon source for microbial lipid production. They can be utilized by oleaginous yeasts to produce and store fatty acids in form of intracellular lipid bodies. In this work, Yarrowia lipolytica growth and substrate consumption were evaluated using the major VFAs present in anaerobic effluents. Individual VFAs as well as synthetic mixtures were tested at different concentrations to determine uptake rates and potential toxicity. Increasing VFA chain length resulted in greater biomass yield although, when added individually, 4 g Carbon/L VFA (e.g. 6.45 g/L of caproic and 10 g/L of acetic acid) caused inhibitory effects. Remarkably, biomass growth increased by 2.5-fold on real anaerobic fermentation effluent compared with synthetic mixtures. When real digestate was supplemented with synthetic VFAs up to 26.5 g/L, the inhibitory effect of the acids was counterbalanced. The results provided evidence of robustness of Y. lipolytica towards low-cost fermentation effluents and present this yeast as a promising candidate for the sustainable production of microbial oil using real digestates.

[The impact of «faster aspart¼ on blood glucose control in children and adolescents with type 1 diabetes treated using a sensor-augmented insulin pump]. / Impacto de faster aspart sobre el control glucémico en niños y adolescentes con diabetes tipo 1 en tratamiento con un sistema integrado.

BACKGROUND AND AIMS: Post-prandial glucose control is essential to achieve metabolic goals in patients with type 1 diabetes mellitus (T1DM). The new «faster aspart¼ insulin has a pharmacological profile noted for its faster absorption and onset of action, and increased early availability, resulting in improved blood glucose control after meals. The main objective of the study was to analyse the efficacy of «faster aspart¼ vs. «insulin aspart¼ in children and adolescents with DM1 on sensor-augmented pump treatment. PATIENTS AND METHODS: Multicentre, longitudinal and prospective analytical trial evaluating the use of faster aspart insulin for three months in children with T1DM with MiniMed640G® sensor-augmented pumps previously treated with aspart insulin. At the beginning and end of the study the following variables were analysed for subsequent comparison: mean sensor glucose, percentage of time in range, hypoglycaemia and hyperglycaemia, area under the curve (AUC) < 70 and > 180 mg/dL, mean sensor glucose pre and postprandial in main meals, daily insulin requirements, basal/bolus percentage, and HbA1c. Acute complications, adverse events and satisfaction survey were assessed. RESULTS: The study included 31 patients with a mean of 13.49 ± 2.42 years of age and with T1DM of 7.0 ± 3.67 years of onset. The use of faster aspart was associated with lower time in hyperglycaemia > 180 mg/dL (25.8 ± 11.3 vs. 22.4 ± 9.5; p = 0.011) and > 250 mg/dL (5.2 ± 4.9 vs. 4.0 ± 3.6; p = 0.04), lower AUC > 180 mg/dL (10.8 ± 6.5 vs. 9.3 ± 6.1; p = 0.03), and increased time in range (71.4 ± 10.0 vs. 74.3 ± 9.2; p = 0.03). No significant changes in hypoglycaemia, HbA1c, insulin requirements, and basal/bolus percentages were detected. Faster aspart was safe and well-evaluated by patients and caregivers. CONCLUSIONS: Faster aspart achieves better glycaemic control by increasing glucose time in range in children and adolescents with T1DM on treatment with sensor-augmented pumps.