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Lipase‐catalyzed transesterification of triglycerides and alcohols to obtain biodiesel is an environmentally friendly and sustainable route for fuels production since, besides proceeding in mild reaction conditions, it allows for the use of low‐cost feedstocks that contain water and free fatty acids, for example non‐edible oils and waste oils. This review article reports recent advances in the field and focus in particular on a major issue in the enzymatic process, the inactivation of most lipases caused by methanol, the preferred acyl acceptor used for alcoholysis. The recent results about immobilization of enzymes on nano‐materials and the use of whole‐cell biocatalysts, as well as the use of cell‐surface display technologies and metabolic engineering strategies for microbial production of biodiesel are described. It is discussed also insight into the effects of methanol on lipases obtained by modeling approaches and report on studies aimed at mining novel alcohol stable enzymes or at improving robustness in existing ones by protein engineering.

Biotechnology can greatly improve the efficiency of forest tree breeding for the production of biomass, energy, and materials. However, EU regulations impede the market introduction of genetically modified (GM) trees so their socioeconomic and environmental benefits are not realized. European policy makers should concentrate on a science-based regulatory process.

The aqueous extraction of orange peel waste (OPW), the byproduct of the juice extraction process generated annually in massive amounts (21 Mton), yields a carbohydrate-rich liquid fraction, termed orange peel extract (OPE). Several studies highlight that the combination of glycerol, a biodiesel byproduct, with carbohydrate mixtures might boost microbial lipid production. This study performed first a shaken flask screening of 15 oleaginous yeast strains based on their growth and lipid-producing abilities on OPE- and glycerol-based media. This screening enabled the selection of R. toruloides NRRL 1091 for the assessment of the process transfer in a stirred tank reactor (STR). This assessment relied, in particular, on either single- and double-stage feeding fed-batch (SSF-FB and DSF-FB, respectively) processes where OPE served as the primary medium and nitrogen-containing glycerol-OPE mixtures as the feeding one. The continuous supply mode at low dilution rates (0.02 and 0.01 h-1 for SSF-FB and DSF-FB, respectively) starting from the end of the exponential growth of the initial batch phase enabled the temporal extension of biomass and lipid production. The SSF-FB and DSF-FB processes attained high biomass and lipid volumetric productions (LVP) and ensured significant lipid accumulation on a dry cell basis (YL/X). The SSF-FB process led to LVP of 20.6 g L-1 after 104 h with volumetric productivity (r L) of 0.20 g L-1 h-1 and YL/X of 0.80; the DSF-FB process yielded LVP, r L and YL/X values equal to 15.92 g L-1, 0.11 g L-1 h-1 and 0.65, respectively. The fatty acid profiles of lipids from both fed-batch processes were not significantly different and resembled that of Jatropha oil, a vastly used feedstock for biodiesel production. These results suggest that OPE constitutes an excellent basis for the fed-batch production of R. toruloides lipids, and this process might afford a further option in OPW-based biorefinery.

In this work, 30 microalgae strains from 17 genera were investigated in regard to biomass productivity in photoautotrophic growth conditions, lipid amount, lipid quality and biomass degradability. Six strains could be identified with robust phototrophic growth properties and high biomass productivities equal or above 300 mg l(-1) day(-1). Anaerobic fermentation of the algal biomass was most efficient for the marine members of the genera Dunaliella and Navicula, while biogas production with the freshwater strains generally resulted in lower methane yields. Monoraphidium contortum was identified as promising candidate for liquid biofuel production, characterized by high biomass productivity during maximum growth (maximum increase of 896 mg dry biomass weight (DW) l(-1) day(-1)) and a promising lipid profile. Neutral lipid production was strongly induced in M. contortum by nitrogen deficient conditions and accumulated to up to 20.4±2.2% of DW.

Abstract Offshore cultivation of seaweed provides an innovative feedstock for biobased products supporting blue growth in northern Europe. This paper analyzes two alternative exploitation pathways: energy and protein production. The first pathway is based on anaerobic digestion of seaweed which is converted into biogas, for production of electricity and heat, and digestate, used as fertilizer; the second pathway uses seaweed hydrolysate as a substrate for cultivation of heterotrophic microalgae. As a result the seaweed sugars are consumed while new proteins are produced enhancing the total output. We performed a comparative Life Cycle Assessment of five scenarios identifying the critical features affecting resource efficiency and environmental performance of the systems with the aim of providing decision support for the design of future industrial scale production processes. The results show that all scenarios provide environmental benefits in terms of mitigation of climate change, with biogas production from dried Laminaria digitata being the most favorable scenario, quantified as −18.7*10 2 kg CO 2 eq./ha. This scenario presents also the lowest consumption of total cumulative energy demand, 1.7*10 4 MJ/ha, and even resulting in a net reduction of the fossil energy fraction, −1.9*10 4 MJ/ha compared to a situation without seaweed cultivation. All scenarios provide mitigation of marine eutrophication thanks to bioextraction of nitrogen and phosphorus during seaweed growth. The material consumption for seeded lines has 2–20 times higher impact on human toxicity (cancer) than the reduction achieved by energy and protein substitution. However, minor changes in cultivation design, i.e. use of stones instead of iron as ballast to weight the seeded lines, dramatically reduces human toxicity (cancer). Externalities from the use of digestate as fertilizer affect human toxicity (non-cancer) due to transfer of arsenic from aquatic environment to agricultural soil. However concentration of heavy metals in digestate does not exceed the limit established by Danish regulation. The assessment identifies seaweed productivity as the key parameter to further improve the performance of the production systems which are a promising service provider of environmental restoration and climate change mitigation.

Recent years have seen a proliferation of studies that use archetype analysis to better understand and to foster transitions toward sustainability. This growing literature reveals a common methodological ground, as well as a variety of perspectives and practices. In this paper, we provide an historical overview of the roots of archetype analysis from ancient philosophy to recent sustainability science. We thereby derive core features of the archetype approach, which we frame by eight propositions. We then introduce the Special Feature, “Archetype Analysis in Sustainability Research,” which offers a consolidated understanding of the approach, a portfolio of methods, and quality criteria, as well as cutting-edge applications. By reflecting on the Special Feature’s empirical and methodological contributions, we hope that the showcased advances, exemplary applications, and conceptual clarifications will help to design future research that contributes to collaborative learning on archetypical patterns leading toward sustainability. The paper concludes with an outlook highlighting central directions for the next wave of archetype analyses.

Abstract Biofuels and the oleochemical industry are highly dependent on plant oils for the generation of renewable product lines. Consequently, production of plant lipids, such as palm and rapeseed oil, for industrial applications competes with agricultural activity and is associated with a negative environmental impact. Additionally, established chemical routes for upgrading bio-lipids to renewable products depend on metal-containing catalysts. Metal leaching during oil processing results in heavy metal contaminated process wastewater. This water is difficult to remediate and leads to the loss of precious metals. Therefore, the biofuels and chemical industry requires sustainable solutions for production and upgrading of bio-lipids. With regard to the former, a promising approach is the fermentative conversion of abundant, low-value biomass into microbial, particularly yeast-based lipids. This study describes the holistic, value-adding conversion of underexploited, macroalgae feedstocks into yeast oil, animal feed and biosorbents for metal-based detoxification of process wastewater. The initial step comprises a selective enzymatic liquefaction step that yields a supernatant containing 62.5% and 59.3% (w/dwbiomass) fermentable sugars from L. digitata and U. lactuca, respectively. By dispensing with chemical pretreatment constraints, we achieved a 95% (w/w) glucose recovery. Therefore, the supernatant was qualified as a cultivation media without any detoxification step or nutrition addition. Additionally, the hydrolysis step provided 27–33% (w/dwbiomass) of a solid residue, which was qualified as a metal biosorbent. Cultivation of the oleaginous yeast C. oleaginosus on the unprocessed hydrolysis supernatant provided 44.8 g L−1 yeast biomass containing 37.1% (w/dwbiomass) lipids. The remaining yeast biomass after lipid extraction is targeted as a performance animal feed additive. Selectivity and capacity of solid macroalgae residues as biosorbents were assessed for removal and recycling of rare and heavy metals, such as Ce+3, Pb+2, Cu+2 and Ni+2 from model wastewater. The biosorption capacity of the macroalgae residues (sorption capacity ∼ 0.7 mmol g−1) exceeds that of relevant commercially available adsorption resins and biosorbents. To facilitate the integration of our technology in existing chemical and biotechnological production environments, we have devised simple, rapid and cost-efficient methods for monitoring both lipogenesis and metal sorption processes. The application of the new optical monitoring tools is essential to determine yeast cell harvesting times and biosorption capacities respectively. For the first time we report on a waste-free bioprocess that combines sustainable, microbial lipid production from low value marine biomass with in-process precious metal recycling options. Our data allowed for a preliminary economic analysis, which indicated that each product could be cost competitive with current market equivalents. Hence, the synaptic nature of the technology platform provides for the economic and ecologic viability of the overall process chain.