Carboxylic platform for the integrated anaerobic / aerobic bioconversion of C02-containing gases into lipids and carotenoids

Abstract

The present doctoral thesis introduces an integrated biotechnological framework for the bioconversion of Ct-gases (CO, CO2) into high-value products, specifically microbial oils and β carotene. Utilizing acetogenic bacteria such as Acetobacterium troodii, Clostridium carboxidivorans and Clostridium ace/(cum, the research demonstrates the bioconversion of Ci- gases into acetic acid via the Wood-Ljiingdahl pathway. This acetic acid serves as a substrate for oleaginous yeasts like Rhodosporidium toruloides and engineered Yarrotria lipolytica strains, which accumulate lipids and β-carotene. The work encompasses a comprehensive analysis of bioreactor configurations, substrate toxicity, and metabolic pathways, revealing optimal conditions for lipid and β-carotene production. The lipid profile predominantly consists of C18:1, C16:0, and C18:2 fatty acids, suitable for biodiesel applications. The research also delves into substrate-dependent variations in metabolite production, emphasizing the role of acetic acid as a cost-effective and sustainable substrate. The study culminates in the optimization of bioprocess configuration, achieving a lipid content peak of 46.9% in the continuous system and a β-carotene concentration of 1357.6 mg/L in the semi-continuous system. This research offers a promising avenue for the sustainable production of biofuels and nutraceuticals from greenhouse gases, thereby contributing to climate change mitigation.