Large‐scale production of diesel‐like biofuels – process design as an inherent part of microorganism development

Abstract

Industrial biotechnology is playing an important role in the transition to a bio-based economy. Currently, however, industrial implementation is still modest, despite the advances made in microorganism development. Given that the fuels and commodity chemicals sectors are characterized by tight economic margins, we propose to address overall process design and efficiency at the start of bioprocess development. While current microorganism development is targeted at product formation and product yield, addressing process design at the start of bioprocess development means that microorganism selection can also be extended to other critical targets for process technology and process scale implementation, such as enhancing cell separation or increasing cell robustness at operating conditions that favor the overall process. In this paper we follow this approach for the microbial production of diesel-like biofuels. We review current microbial routes with both oleaginous and engineered microorganisms. For the routes leading to extracellular production, we identify the process conditions for large scale operation. The process conditions identified are finally translated to microorganism development targets. We show that microorganism development should be directed at anaerobic production, increasing robustness at extreme process conditions and tailoring cell surface properties. All the same time, novel process configurations integrating fermentation and product recovery, cell reuse and low-cost technologies for product separation are mandatory. This review provides a state-of-the-art summary of the latest challenges in large-scale production of diesel-like biofuels.

Process Design and Economics for the Conversion of Lignocellulosic Biomass to Hydrocarbons: Dilute-Acid and Enzymatic Deconstruction of Biomass to Sugars and Biological Conversion of Sugars to Hydrocarbons

“…As noted above, the FFA material is assumed for modeling purposes to consist of palmitate (palmitic acid), a fully saturated 16-carbon fatty acid; in reality, the FFA material will likely consist of a mixture of saturated and unsaturated fatty acids in the diesel carbon number range (C12-C20) [83]. These components will largely exhibit similar properties as palmitic acid, namely low density relative to water (palmitate density = 0.86 kg/L) and essentially immiscible with water.…”

“…Reasonable minima and maxima for each variable were chosen to understand and quantify the resulting cost impact on overall MFSP. Each variable was changed to its maximum 83 and minimum value with all other factors held constant. The sensitivities of (a) MFSP and (b) product yield are displayed as tornado charts in Figure 20.…”

Bioprocess Engineering for Microbial Synthesis and Conversion of Isoprenoids

“…Most proof-of-concept research projects focus on only one or a couple of aspects of a bioprocess, thereby separating the microorganism and the isoprenoid synthesis or the conversion from the rest of the process design and neglecting demands of largescale operations for certain organism properties [23]. In addition to those microorganism properties generally desirable from a bioprocess-oriented viewpoint, such as the ability to use low-cost feedstocks, tolerance to extreme conditions, or resistance to inhibitors, isoprenoid bioprocesses would benefit from biocatalysts with low-emulsion-forming tendency and tolerance against organic compounds.…”

“…This would dramatically increase the ease of product recovery in aqueous-organic two-phase systems simply by gravity separation without the need for centrifugation or de-emulsification techniques which further raise process costs [39]. For price competitive "low-cost high-volume" products such as biofuels the possibility of operating a bioprocess in a continuous mode including the possibility of cell reuse is a valuable measure to increase productivity and lower capital cost [23]. A closed bioreactor infrastructure to prevent contaminations operating in batch or fed-batch mode, as is usually the case in laboratory-scale experiments, can significantly increase infrastructure costs and will most likely not be cost-competitive enough at the required scale [102].…”

Editorial: ESBES – European Society of Biochemical Engineering Sciences

“…Maria C. Cuellar et al [3] review the large-scale production of diesel-like biofuels and provide insight to process design that in turn influences strain development. The work of Gruber et al [4] is an interesting example of biocatalysis using native hosts (in this case Candida tenuis and Pichia stipites) as whole-cell catalysts, which significantly shortens process development time.…”