Consolidated bioprocessing with designed co-cultures of Caldicellulosiruptor species

Abstract

About 96% of hydrogen is produced via chemical processes from fossil material globally and just 4% is obtained from environmentally friendly sources. Caldicellulosiruptor species are good candidates for hydrogen production via dark fermentation from a variety of substrates. They therefore provide a great opportunity to be used as decomposers of organic waste, lignocellulosic material and municipal and industrial wastewater for added value metabolites.

For this study, five Caldicellulosiruptor species were used to screen for the best hydrogen producer on lignocellulosic biomass, in this case wheat straw from, a consolidated bioprocessing perspective. The preferred candidate C. kronotskyensis, was then studied further on artificial medium (glucose and xylose). As part of this project, the possibility of hydrogen production was also investigated from different industrial wastewater samples.

Based on the results obtained, C. kronotskyensis was selected as the desired species. Biphasic growth was observed when C. saccharolyticus was grown on wheat straw which is known to be linked to the expression of ABC transporters previously shown in a related study on wheat straw hydrolysate. Comparing results of C. kronotskyensis on artificial medium to a similar study as C. saccharolyticus shed light on the existence of possibly a single group of ABC transporters for C. kronotskyensis with a higher affinity for xylose.

The pure culture for C. owensensis was terminated early as it could not sustain growth on wheat straw after glucose depletion. This finding is confirmed through bioinformatic analysis to be due to the absence of binding proteins called täpirins that mediate attachment to lignocellulosic material. For the fermentability test, positive outcomes were obtained for fibre sludge wastewater sample providing a step forward for subsequent experiments in bioreactor under pH control and growth monitoring conditions.

Popular Abstract

Do you know that hydrogen is currently used in fuel cells to power cars, commercial buses and that it is already gaining attention in aircraft and electronic industries? Do you realize that this hydrogen could be produced from organic waste like wheat straw that is abundantly available? Hydrogen is not just an energy carrier but also an intermediate that is used in the synthesis of ammonia which is a major component of fertilizers. Dependence on natural resources for decades to satisfy energy needs have led to an increased environmental pollution calling for global concerns. One of the United Nation’s target for 2030 is to ensure access to clean, affordable and reliable source of energy using sustainable sources of raw materials for energy production. However, about 96% of hydrogen produced today is from depleting fossil reserves, which are non-renewable.

Investigating hydrogen production from largely available plant-derived waste and industrial wastewater streams is therefore necessary to reduce the dependency on fossil resources. This project was carried out with bacteria of the genus Caldicellulosiruptor that are known to grow at extremely high temperatures in the absence of oxygen. The challenge of this study was to establish the best hydrogen producing bacteria from the above-mentioned genus from a consolidated bioprocessing perspective. As part of the project, possibilities of hydrogen production from three different wastewater samples with the same bacteria were also examined in serum flasks.

Interesting outcomes were obtained for the hydrogen producing candidate C. kronotskyensis as it showed promising results different from the rest of the members in the genus. This finding opens doors for improving hydrogen productivity which has been a rate limiting parameter in previous studies with these bacteria. Positive results were also obtained for one of the wastewater samples (fibre sludge) hence providing the way forward for subsequent experiments in laboratory scale reactors for pH control and bacteria growth monitoring.

• author: Neba Nubong, Pride Afah
• supervisor: Thitiwut Vongkumpeang
• organization: Applied Microbiology; Biotechnology
• course: KMBM01 20181
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Consolidated bioprocessing, co-cultures, pure cultures, Caldicellulosiruptor sps, applied biotechnology, teknisk mikrobiologi
• language: English
• id: 8946659
• date added to LUP: 2018-06-18 14:35:53
• date last changed: 2018-11-26 09:17:47