Synthesis and analysis of separation networks for the recovery of intracellular chemicals generated from microbial-based conversions

Abstract

BackgroundBioseparations can contribute to more than 70% in the total production cost of a bio-based chemical, and if the desired chemical is localized intracellularly, there can be additional challenges associated with its recovery. Based on the properties of the desired chemical and other components in the stream, there can be multiple feasible options for product recovery. These options are composed of several alternative technologies, performing similar tasks. The suitability of a technology for a particular chemical depends on (1) its performance parameters, such as separation efficiency; (2) cost or amount of added separating agent; (3) properties of the bioreactor effluent (e.g., biomass titer, product content); and (4) final product specifications. Our goal is to first synthesize alternative separation options and then analyze how technology selection affects the overall process economics. To achieve this, we propose an optimization-based framework that helps in identifying the critical technologies and parameters.ResultsWe study the separation networks for two representative classes of chemicals based on their properties. The separation network is divided into three stages: cell and product isolation (stage I), product concentration (II), and product purification and refining (III). Each stage exploits differences in specific product properties for achieving the desired product quality. The cost contribution analysis for the two cases (intracellular insoluble and intracellular soluble) reveals that stage I is the key cost contributor (>70% of the overall cost). Further analysis suggests that changes in input conditions and technology performance parameters lead to new designs primarily in stage I.ConclusionsThe proposed framework provides significant insights for technology selection and assists in making informed decisions regarding technologies that should be used in combination for a given set of stream/product properties and final output specifications. Additionally, the parametric sensitivity provides an opportunity to make crucial design and selection decisions in a comprehensive and rational manner. This will prove valuable in the selection of chemicals to be produced using bioconversions (bioproducts) as well as in creating better bioseparation flow sheets for detailed economic assessment and process implementation on the commercial scale.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-017-0804-2) contains supplementary material, which is available to authorized users.

Simultaneous lipid biosynthesis and recovery for oleaginous yeast Yarrowia lipolytica

“…The feasibility of these intracellular metabolite production processes eventually depends on the efficiency of the down-streaming for complete product recovery. Existing methodologies for intracellular oil recovery are based on energy-intense cell-disruptive techniques which account for about 70% of total production costs [7]. While, others suggest direct hydro-thermal conversions of the oleaginous cells into liquefied high energy drop-in fuel precursors [8].…”

Synthesis and analysis of separation processes for extracellular chemicals generated from microbial conversions

“…We will use the abbreviations when referring to the specific technologies hereafter. For discussions regarding the three stage scheme and the specific separation technologies, the readers are referred to [42,50,51]. We would like to point out that we have chosen the most basic configurations for the technology models.…”

“…The active streams are shown by bold red lines and selected technologies are highlighted in different colors corresponding to each stage: red for stage I, green for stage II, and blue for stage III. Cost distribution is shown by the numbers on the left bar the previous study on intracellular products [51], the major cost driver was Stage I irrespective of the other properties of the product, however, for extracellular products, Stage II costs take precedence and have a major impact on the overall downstream separation network selection.…”

“…For a volatile (VOL) product, the product will be obtained at the top instead of at the bottom in Dst. Also, direct Dst is typically cheaper than Ext or Atpe when the relative volatility is greater than 1.05 [51,113]. For a specialty (SPC) product, the same argument about additional purification and stringent requirements in Stage III technologies will be valid due to high purity requirements.…”

“…However, these studies were mostly focused on either general methodological discussions or analysis for specific products on a case-by-case basis. The recent studies by Maravelias group [42,50,51] have presented a systematic approach for generating and modeling bio-separation superstructures for different classes of products defined in terms of a set of attributes including product localization, solubility, density, volatility, physical state, and intended use. This work builds on those recent studies to look at microbial products released extracellularly in more detail through carefully selected case studies, appropriate parameter values, typical range of variation and additional insights derived from solving multiple optimization problems.…”