Model-based biotechnological potential analysis of Kluyveromyces marxianus central metabolism

Funding Information: The research was supported by ERDF project Nr. 2DP/2.1.1.1.0/14/APIA/VIAA/043. Publisher Copyright: © 2017, Society for Industrial Microbiology and Biotechnology.The non-conventional yeast Kluyveromyces marxianus is an emerging industrial producer for many biotechnological processes. Here, we show the application of a biomass-linked stoichiometric model of central metabolism that is experimentally validated, and mass and charge balanced for assessing the carbon conversion efficiency of wild type and modified K. marxianus. Pairs of substrates (lactose, glucose, inulin, xylose) and products (ethanol, acetate, lactate, glycerol, ethyl acetate, succinate, glutamate, phenylethanol and phenylalanine) are examined by various modelling and optimisation methods. Our model reveals the organism’s potential for industrial application and metabolic engineering. Modelling results imply that the aeration regime can be used as a tool to optimise product yield and flux distribution in K. marxianus. Also rebalancing NADH and NADPH utilisation can be used to improve the efficiency of substrate conversion. Xylose is identified as a biotechnologically promising substrate for K. marxianus.publishersversionPeer reviewe

System Dynamics Model Analysis of Pathway to 4th Generation District Heating in Latvia

In the article, a possibility to introduce the 4th generation district heating (4GDH) in Latvia is analyzed with the system dynamic modeling. Three policy instruments were included into the system dynamic model: subsidies, instrument for risk reduction and instrument for efficiency increase, and their impact on the system operation was analyzed. Six development scenarios are examined in the article, two of which are supplemented with the transition of heat network to the low-temperature regime at a different share of the renewable energy (60%, 80%, 95%). The heat tariff was used as the main indicator determining the pace and structure of the technology change. In the model the existing natural gas technology was included and three technologies of the renewable energy – biomass combustion equipment, solar collectors with the accumulation and heat pumps. Results of the modeling shows that scenario, at which no policy instruments are used, reduce CO2 emissions for 58.6% until 2030; but it is possible to achieve a zero emission level, in case political instruments are used