Jeanne Louw

The study identified process development priorities toward the feasible production of five value‐added biochemicals in a sugarcane biorefinery based on achievable bioconversion performances. Multiple process scenarios using A‐molasses as feedstock were simulated in Aspen Plus® via direct microbial conversions. Techno‐economic and carbon footprint analyses were conducted using full factorial design (FFD) to couple fermentation performance with key viability indicators, and Monte Carlo simulation was used to assess financial uncertainty. 3‐Hydroxypropanoic acid (3‐HP) and 2,3‐butanediol emerged as promising candidates for short‐term deployment, with current technology performances showing acceptable cost of production compared with market prices reporting internal rates of return of 45.7 and 26.6%, respectively. Adipic acid should be prioritized for medium‐term development as minimal improvements from current bioconversion efficiencies were required to achieve commercial competitiveness according to the factorial design. Acrylic acid (AA) showed the highest potential for profitability in the long‐term, with potential selling prices of $788–1397 t ⁻¹ _AA , but required order of magnitude technology improvements to achieve it. Alternatively, AA production from sugar‐derived 3‐HP, which could achieve up to 43.0% lower minimum selling prices and 73.4% less greenhouse gas emissions compared with fossil‐based methods, should be prioritized for medium‐term deployment of AA. Technically achievable performances for all five products indicated potential to meet financial targets for supplanting their fossil‐based equivalents, at a significantly lower carbon footprint, justifying ongoing investment in strain and bioprocess development.

Adipic acid (ADA) is a highly valuable industrial dicarboxylic acid used largely as a precursor of nylon 6,6 production. It is currently synthesized via a petrochemical process that accounts for over 80% of the global industrial N2O emissions. Biobased ADA offers a cleaner alternative but requires technological advancements in microbe and bioprocess performance to be commercially relevant. An in-depth feasibility analysis was conducted to evaluate two biobased pathways for the production of ADA, modeled as integrated sugarcane biorefineries in Aspen Plus®. The pathways examined were: (1) direct fermentation of sugars to ADA (S1-ADA) and (2) hydrogenation of biobased cis,cis-muconic acid to ADA (S2-ccMA-ADA). The impact of improvements to key bioprocess metrics (product yield, titer, and volumetric productivity) on the minimum selling price and greenhouse gas (GHG) emissions for both pathways was also evaluated in a full-factorial study. S1-ADA demonstrated the highest feasibility potential, achieving minimum selling prices and GHG emissions that were 33.3% and 78.7% lower, respectively, than those of fossil-based production. These results were obtained under conditions of optimal strain performance and bioprocess efficiencies. However, under comparable technological advancements, the best-achievable results for S2-ccMA-ADA indicated a green premium of 13.4% alongside a 68.4% reduction in emissions compared to the fossil-based product. Consequently, the direct biobased pathway (S1-ADA) shows greater potential to compete with and eventually replace its fossil-based counterpart once optimized. This finding highlights the need to prioritize S1-ADA for further biotechnological development.

Production of acrylic acid (AA) via direct microbial conversion of sugars may offer substantial economic and environmental benefits compared to indirect sugars conversion via chemical intermediates. However, further improvements to the performances of direct microbial bioconversions are required to allow industrial large-scale implementation. The benefits in terms of minimum selling price (MSP) and greenhouse gas (GHG) emissions associated with such improvements to bioprocess performances were assessed through a Full-factorial (FF) assessment. Aspen Plus® simulations of direct sugars conversion to AA in a biorefinery retrofitted to a typical sugarcane mill were built using either conventional fermentation (S1-AA-CF) or extractive fermentation (S2-AA-EF). At current-best performances the MSP of S2-AA-EF is 25 times lower than for S1-AA-CF, while having 97.5% fewer GHG emissions. The lowest achievable MSPs from feasible improvements to microbe and bioprocess performances for S1-AA-CF and S2-AA-EF were 65.4% and 29.6% below the fossil-based price, respectively. The desired performance of the conventional fermentation route is dependent on strain engineering to alleviate AA product-inhibition, allowing for titres of 52 g_AA. L⁻¹ or more to be achieved in a fed-batch bioprocess. Thus, extractive fermentation is recommended as the preferred route for direct microbial conversion of sugars to AA. Graphical Abstract