Recent advances on the catalytic conversion of waste cooking oil

The recovery of waste cooking oil has long been known for second life uses without chemical modification. However, the concepts of bioeconomy and circular economy are much more recent and include a ranges of tasks such as recovery, storage, use, chemical modification. International research into the use of modified and unmodified waste cooking oil and their potential uses has been the subject of incessant research in both academia and industry. The main purpose of this review is to present the recent breakthroughs obtained in the field of recovery of used cooking oils for the last decade. The review discusses advances obtained in major production pathways recently explored splitting in the following categories: (i) transesterification of waste cooking oil including biodiesel production with heterogeneous/homogeneous base and acid catalysis, magnetic heterogeneous catalysis, biocatalysis and alternative technologies such as electrolysis, continuous flow, microwave irradiation, ultrasound irradiation; (ii) transesterification of waste cooking oil including catalytic biolubricant production; (iii) interesterification; (iv) hydrolysis and (v) hydrodeoxygenation, hydrocracking and hydrogenation. This review also briefly overviews current understanding of waste cooking oil valorization and the underpinning mechanism

Life cycle analysis of fermentative production of succinic acid from bread waste

According to the US Department of Energy, succinic acid (SA) is a top platform chemical that can be produced from biomass. Bread waste, which has high starch content, is the second most wasted food in the UK and can serve as a potential low cost feedstock for the production of SA. This work evaluates the environmental performance of a proposed biorefinery concept for SA production by fermentation of waste bread using a cradle-to-factory gate life cycle assessment approach. The performance was assessed in terms of greenhouse gas (GHG) emissions and non-renewable energy use (NREU). Waste bread fermentation demonstrated a better environmental profile compared to the fossil-based system, however, GHG emissions were about 50% higher as compared to processes using other biomass feedstocks such as corn wet mill or sorghum grains. NREU for fermentative SA production using waste bread was significantly lower than fossil-based system and about the same as that of established biomass-based processes, thus proving the great potential of waste bread as a valuable feedstock for bioproduction of useful chemicals. The results show that steam and heating oil used in the process were the biggest contributors to the NREU and GHG emissions. Sensitivity analyses highlighted the importance of the solid biomass waste generated in the process which can potentially be used as fish feed. The LCA analysis can be used for targeted optimization of SA production from bread waste, thereby enabling the utilization of an otherwise waste stream and leading to the establishment of a circular economy

Bioproduction of succinic acid from xylose by engineered Yarrowia lipolytica without pH control

Background Xylose is the most prevalent sugar available in hemicellulose fraction of lignocellulosic biomass (LCB) and of great interest for the green economy. Unfortunately, most of the cell factories cannot inherently metabolize xylose as sole carbon source. Yarrowia lipolytica is a non-conventional yeast that produces industrially important metabolites. The yeast is able to metabolize a large variety of substrates including both hydrophilic and hydrophobic carbon sources. However, Y. lipolytica lacks effective metabolic pathway for xylose uptake and only scarce information is available on utilization of xylose. For the economica feasibility of LCB-based biorefineries, effective utilization of both pentose and hexose sugars is obligatory. Results In the present study, succinic acid (SA) production from xylose by Y. lipolytica was examined. To this end, Y. lipolytica PSA02004 strain was engineered by overexpressing pentose pathway cassette comprising xylose reductase (XR), xylitol dehydrogenase (XDH) and xylulose kinase (XK) gene. The recombinant strain exhibited a robust growth on xylose as sole carbon source and produced substantial amount of SA. The inhibition of cell growth and SA formation was observed above 60 g/L xylose concentration. The batch cultivation of the recombinant strain in a bioreactor resulted in a maximum biomass concentration of 7.3 g/L and SA titer of 11.2 g/L with the yield of 0.19 g/g. Similar results in terms of cell growth and SA production were obtained with xylose-rich hydrolysate derived from sugarcane bagasse. The fed-batch fermentation yielded biomass concentration of 11.8 g/L (OD600: 56.1) and SA titer of 22.3 g/L with a gradual decrease in pH below 4.0. Acetic acid was obtained as a main by-product in all the fermentations. Conclusion The recombinant strain displayed potential for bioconversion of xylose to SA. Further, this study provided a new insight on conversion of lignocellulosic biomass into value-added products. To the best of our knowledge, this is the first study on SA production by Y. lipolytica using xylose as a sole carbon source

Fermentative production of 2,3-Butanediol using bread waste – A green approach for sustainable management of food waste

Bread is Europe’s most wasted food, and the second most wasted food after potatoes in UK. Bread waste (BW) is a clean source of high-quality fermentable sugars. In this study, the potential of Enterobacter ludwigii to accumulate 2,3-butanediol (BDO) from BW was evaluated. Initially, the optimal inoculum size and yeast extract concentration were determined, followed by extraction of sugars from BW using acid and enzymatic hydrolysis. A glucose yield of 330–530 g/kg BW was obtained, and the sugars released were utilised for BDO production by E. ludwigii. The fed-batch cultivation using pure glucose and glucose rich hydrolysates from acid and enzymatic hydrolysis resulted in BDO titres of 144.5, 135.4, and 138.8 g/L, after 96 h, with yield of 0.47, 0.42 and 0.48 g/g yield, respectively. The innovation of the work is valorisation of BW to BDO with a circular biorefining approach and thus, reducing BW disposal and associated environmental burden

Cytochrome P450-mediated co-metabolism of fluoroquinolones by Haematococcus lacustris for simultaneously promoting astaxanthin and lipid accumulation

Microalgae-based antibiotic removal treatment has attracted attention because of its low carbon and sustainable advantages. The microalgal co-metabolism system with a suitable carbon source leads to enhanced performance of pollutant removal. However, currently, limited knowledge is available for the removal of fluoroquinolone using a microalgae-mediated co-metabolism system. In this study, we first investigated that the biotic processes by alga Haematococcus lacustris in the co-metabolism system by adding glycerol would be the main contributors responsible for the removal of 10 mg/L ofloxacin (OFL) with the efficiency of 79.73% and the removal of 10 mg/ L enrofloxacin (ENR) with the efficiency of 54.10%, respectively. Furthermore, we found that pyruvate from glycerol was converted into substrates and precursors, thereby resulting in the significant accumulations of microalgal astaxanthin and lipid. The astaxanthin content of H. lacustris was achieved at 4.81% and 4.69% treated with OFL and ENR in the presence of glycerol, with 16.04% and 14.55% of lipid content, respectively. The proposed metabolites and pathways were identified to plausibly explain the biodegradation of fluoroquinolone by H. lacustris. The molecular analyses demonstrated that cytochrome P450 (CYP450) enzymes are responsible for the biodegradation of fluoroquinolone, and it was further verified that fluoroquinolones might insert into CYP450 to finally form an efficient and tight binding conformation by molecular dynamic simulation. These findings provide a microalgae-based route for feasible and sustainable biodegradation of antibiotics using a co-metabolism strategy comprising glycerol as a carbon source, with the synergistic accumulation of valuable products.peer-reviewe

A combined light regime and carbon supply regulation strategy for microalgae-based sugar industry wastewater treatment and low-carbon biofuel production to realise a circular economy

The replacement of fossil fuels with clean and renewable biofuels is of both research and market interest for realising a circular economy. However, microalgae-based biofuels have shown promise as alternative low-carbon biofuels to other crop-based biofuels, some key obstacles in their production remain to be addressed, such as high costs and low lipid productivity. In this study, a Chlorella sp. CSH4 was cultivated using a combined light regime and carbon supply regulation strategy to enhance sugar industrial wastewater bioremediation, biomass accumulation and lipid production. Blue light irradiance of 200 μmol photons m -2 s-1 together with 10 g/L glucose and 9.2 g/L glycerol supply was found to effectively enhance the biomass accumulation and pollutant-removal capacity of Chlorella sp. during the growth phase and its lipid production during the stationary phase. Furthermore, the biodiesel properties of the lipid retrieved from Chlorella sp., as demonstrated by its fatty acid profile, were found to be suitable for commercial application. Possible mechanisms were explored to explain how this combined strategy caused this microalga to exhibit highly efficient biomass and lipid production together with efficient pollutant removal. Moreover, upscaled semi-continuous treatment using both sugar industry wastewater and negligible carbon sources (e.g., food waste hydrolysate and crude glycerol) with a mass balance analysis was conducted to initially validate the feasibility of applying our combined strategy for microalgae based wastewater treatment. In sum, this study demonstrated the feasibility of cultivating a microalga using a combined strategy comprising a light regime and carbon supply regulation to achieve both wastewater treatment and low-carbon biofuel production.peer-reviewe

Sustainable biosurfactant production from secondary feedstock—recent advances, process optimization and perspectives

Biosurfactants have garnered increased attention lately due to their superiority of their properties over fossil-derived counterparts. While the cost of production remains a significant hurdle to surpass synthetic surfactants, biosurfactants have been anticipated to gain a larger market share in the coming decades. Among these, glycolipids, a type of low-molecular-weight biosurfactant, stand out for their efficacy in reducing surface and interfacial tension, which made them highly sought-after for various surfactant-related applications. Glycolipids are composed of hydrophilic carbohydrate moieties linked to hydrophobic fatty acid chains through ester bonds that mainly include rhamnolipids, trehalose lipids, sophorolipids, and mannosylerythritol lipids. This review highlights the current landscape of glycolipids and covers specific glycolipid productivity and the diverse range of products found in the global market. Applications such as bioremediation, food processing, petroleum refining, biomedical uses, and increasing agriculture output have been discussed. Additionally, the latest advancements in production cost reduction for glycolipid and the challenges of utilizing second-generation feedstocks for sustainable production are also thoroughly examined. Overall, this review proposes a balance between environmental advantages, economic viability, and societal benefits through the optimized integration of secondary feedstocks in biosurfactant production