Immobilization of Calidocellulosiruptor species mediated by chitosan

Abstract

Caldicellulosiruptor species are regarded as the best microorganisms to produce hydrogen due to their ability to break down many types of sugars and hydrogen yields near the theoretical maximum. The major drawback is their low volumetric hydrogen productivity (QH2), which makes the current process setup economically non-viable. In this study, the natural capability of Caldicellulosiruptor species were exploited, i.e., through biofilm formation in the presence of a natural polymer called chitosan in a CSTR to achieve higher QH2.
Co-cultures of C. saccharolyticus and C. owensensis were used to perform a continuous cultivation with two conditions (with and without chitosan). The QH2 was higher in case of the cultivation without chitosan that lasted until D= 0.7 h-1, but in case of cultivation with chitosan the QH2 was slightly lower, which lasted until D=0.9 h-1. Biofilm formation was observed in both the cases from D= 0.2 h-1 onwards. Properties of chitosan such as antimicrobial activity, solubility and degradation were investigated and applied during the study.
To sum up, chitosan has the potential to increase the QH2 levels but not solely. However, it needs to be combined with other factors, such as another reactor configuration, and additional carrier materials to aid in improving the QH2.

Popular Abstract

Heavy reliance on the petroleum based fuels has rapidly increased the levels of greenhouse gases in the atmosphere which has led to global warming. There is a need for an alternative type of fuel which is clean and environmental friendly. One such fuel that comes up to the mind is hydrogen gas. The combustion of hydrogen gas yields just water which makes it the cleanest fuels. But how can hydrogen be produced?
Caldicellulosiruptor species is regarded as the best microorganism to produce hydrogen due to its ability to break down many types of sugars. The major drawback is its hydrogen productivity which is low, which makes it a non-viable economic process. In this study, the natural capability of Caldicellulosiruptor species was exploited, i.e., biofilm formation along with an addition of a natural polymer called chitosan to achieve higher hydrogen productivity.
Chitosan is a polymer obtained by modification of chitin, which is present in shells of crustacean animals. During the study, few properties of Caldicellulosiruptor species and chitosan were realized. Experiments were conducted by growing the cells in a bioreactor which gave us convincing outcomes such as it is capable of preventing cells to wash out at very high pump rates in a continuous culture process which could be achieved before.
Although chitosan did not aid in increasing the productivity of hydrogen, it did show its capability to attach the cells to themselves or to the chitosan matrix, being the basis to form biofilm. Understanding the chemistry behind chitosan and addition of new materials is the way forward to further develop mature biofilm formation.
Altogether, the knowledge obtained with this study opens up ideas upon different strategies to improve the hydrogen production, which can make it industrially feasible and that in turn helps us preserve the environment as well.

• author: Rao, Nikhil Seshagiri
• supervisor: Thitiwut Vongkumpeang
• organization: Applied Microbiology; Biotechnology
• alternative title: Immobilisering av Calidocellulosiruptor arter medierade av kitosan
• course: KMBM01 20181
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: chitosan, biofilm, applied microbiology, teknisk mikrobiologi
• language: English
• id: 8950736
• date added to LUP: 2018-06-18 16:19:49
• date last changed: 2018-11-26 09:16:21