(690e) From Starch-Enriched Algal Biomass to Biobutanol Production – a Model-Based Optimisation Study

Biobutanol is a sugar-based biofuel produced by the ABE fermentation, an old biochemical process whereby sugars are metabolised into acetone (A), butanol (B), and ethanol (E). The commercial implementation of the ABE fermentation, however, is restricted due to: i) low butanol fermentation yields and ii) the use of common feedstocks which raise food vs fuel concerns (food-based biomass) or compete for arable land (lignocellulosic biomass) (Kumar and Gayen, 2011). Microalgal biomass has the potential to become a sustainable large-scale feedstock suitable for the ABE fermentation due to its ability to accumulate starch (Markou et al., 2012). Nutrient-stressed algal cultivation has been shown to induce starch accumulation, but such a strategy must be optimised to sustain algal growth while simultaneously enhancing starch formation.

In order to establish the best microalgae-to-biobutanol route, we have previously employed a kinetic model capable of accurately predicting algal growth dynamics subject to mixotrophic growing conditions co-limited by nitrogen and phosphorus (Figueroa-Torres et al., 2017). The proposed model was successfully validated against datasets obtained from lab-scale cultures of Chlamydomonas reinhartii CCAP 11/32c. In this work, “starch-enriched” algal biomass, as obtained from a validated model-based cultivation strategy maximising starch formation, has been evaluated as a feedstock for biobutanol production. Thus, a kinetic model has been developed in combination with a range of lab-scale batch fermentation experiments with the wild-type strain Clostridium acetobutylicum DSM 792 (at 37 °C under anaerobic conditions) to: i) identify optimal pre-treatment steps required to use “starch-enriched” microalgal biomass as a fermentable feedstock, ii) establish optimal operating conditions for biobutanol production, and ii), and establish the kinetics of biobutanol production from “starch-enriched” algal biomass.

References

Figueroa-Torres, G.M., Pittman, J.K., Theodoropoulos, C., 2017. Optimisation of microalgal starch formation for the biochemical production of biobutanol. Comput. Aided Chem. Eng. 40, 2899–2904.

Kumar, M., Gayen, K., 2011. Developments in biobutanol production: New insights. Appl. Energy 88, 1999–2012.

Markou, G., Angelidaki, I., Georgakakis, D., 2012. Microalgal carbohydrates: an overview of the factors influencing carbohydrates production, and of main bioconversion technologies for production of biofuels. Appl. Microbiol. Biotechnol. 96, 631–645.