In English

Media optimisation and valorisation of (crude) glycerol for marine algal biomass production

Johannes Nelles
Göteborg : Chalmers tekniska högskola, 2018. 61 s.
[Examensarbete på avancerad nivå]

Chlorella salina combines a high growth rate and carbohydrate productivity with the advantages of being a fast-sedimenting marine strain. These characteristics hold the potential to make C. salina the host organism of a sustainable and economically viable process of carbohydrate and biomass production. In processes with the currently established methodology, only the production of high value products might me economically sustainable due to the economic and environmental impacts of biomass production. Optimisation of the media composition while maximising biomass production is one way of improving the production of microalgae. This has been carried out in this work in addition to evaluating the valorisation of (crude) glycerol, all in order to evaluate the potential of utilizing C. salina for algal biomass production. The impact of nitrogen source on growth and composition was first evaluated and urea was shown to be a favourable nitrogen-source as it has a lower price and global warming potential than the other tested nitrogen-sources while still yielding a similar performance in terms of biomass productivity. It could be shown that the nitrogen:phosphorus ratio can be increased to at least 48:1 while maintaining the performance of the culture. This yields significant savings on the supply of phosphorous fertilisers. To aid in increasing biomass production, the supply of an organic carbon source was investigated to encourage concurrent heterotrophic metabolism alongside phototrophic growth. Glycerol was selected as the carbon-source and was found to be consumed at 0.5, 1 and 2 g/L in batch cultures, yet did not lead to increased growth or carbohydrate formation. Building on this, a repeated batch mode was applied and showed that batch operation appears to be favourable for biomass production. Continued operation of repeated batch mode with glycerol showed a consumption, but again with no impact on the growth or carbohydrate accumulation. Crude glycerol was also supplied and did not have a significant impact on growth. These results aid in improving the cost-efficiency and decreased environmental impact of a biomass and carbohydrate production process with C. salina. However, there are many more parameters that need to be evaluated on the way to the final process. Examples are the downstream processing costs, evaluation of possible waste streams to use instead of fertilizer nitrogen and phosphorous, by-product formation and possible biomass uses, as well as the scale up. A biorefinery approach by utilization of high-value by-products such as carotenoids should also be considered. Although more steps have been taken in this work, establishing a cost-efficient process for biomass and carbohydrate formation with C. salina still remains a long way.



Publikationen registrerades 2018-09-24.

CPL ID: 256014

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