Likely Costs Of Large Scale Hydroxylation Or Epoxidation Processes With Whole Cell Biocatalysts

To get some idea of the prices to be expected for compounds produced with these approaches, we have estimated the total cost of producing 10,000 tons per annum of 1-octanol from «-octane, based on data collected for this conversion by P. oleovorans, during growth in a two-liquid-phase system containing 15% (v/v) hexadecane as a carrier phase.47 n-Octane is dissolved in the carrier phase to a concentration of 5 -10% (v/v), converted by the P. oleovorans cells in the aqueous phase, and the product 1-octanol dissolves in the hexadecane phase once more. Downstream processing consists of a phase separation, followed by two distillation steps. In the first step, the C8 alkane/alkanol are separated from the hexadecane, which is recycled into the bioreactor. In the second step, the n-octane is distilled off the n-octanol: the octane is recycled to the bioreactor, and the octanol is collected as the desired product. This approach leads to a very clean product stream of >98% pure 1-octanol.48

The total cost of the process was estimated to be about 8 US$ per kg product (Figure 15.13). The most significant cost item (ca. 40% of the total) was due to the glucose and salts necessary to support cell growth; that is, these are part of the biocatalyst formation costs. Biocatalyst costs can be reduced by increasing specific activities per g cells, and by extending the useful lifetime of whole-cell biocatalysts. We estimate that reductions in biocatalyst cost and associated process costs might lower the preceding estimate to 5 US$ per kg product. Although the estimate described here was carried out for a specific

Figure 15.13 Biocatalysis for the oxidation of n-octane to 1-octanol at 10,000 tons/year.

alkane-to-alkanol conversion, it applies to similar hydroxylations or oxidations of other apolar compounds. A key parameter in all such estimates is the specific activity per g cells that can be achieved. Typical activities are in the order of 5 to 50 U/g cell dry mass, where U is the international enzyme activity unit, expressed as mmol of product formed or mmol substrate utilized per minute.

The preceding estimate suggests that products valued at more than 10 US$ per kg are potential targets for biocatalytic production, provided the market is sufficiently large. Clearly, compounds valued at 50-100 US$ or more per kg are interesting biocatalysis targets. However, high tonnage targets of 5-7 US$ per kg are still worth investigating.

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Responses

  • CHRISTIAN
    How epoxidation done on large scale?
    5 years ago

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