Team:Osaka/Project cellulase

Cellulase

In order to create a practical system for Continuous Greening, our micro-organisms have to gain nutrients from dry and poor soil. Therefore we took attention at the planted woods. Microbes particularly decompose dead wood into their own nutrients and thrust by themselves. Wood fibers are made of cellulose, hemi-cellulose, and lignin. Of those, cellulose dominates most of parts. The advantage of cellulose is that it made of 1→4 liked D-glucose; therefore if we can break β bonds between them, our microbes can gain precious nutrients in dry area. Consequently, we focused on degradation of cellulose by secretion of cellulase. Several different enzymes are known as cellulase; endo-glucanase breaks internal bonds in cellulose and exo-glucanse breaks cellulose bonds from exposed ends results in disaccharide called cellobiose. In addition, β-gluctocidase which tears cellobiose into glucose is needed to obtain the final object. We aim to produce these enzymes from our microbe.

In pursuance of getting more active degradation of cellulose, we tried two different experiments. At first, we created BioBrick of each different cellulase domain and be able to place and combine them in different orders. In combination of two or more different proteins, simply called fusion protein, their original ability will cooperate to achieve higher degradation of cellulose. We called this CellulaseBrick. Different placement can be result in different outcome even though their combination is same. We tried several possible alignments and assay them. Second, we looked into different microbes and their ability to break down cellulose. In this year’s project, we tried Escherichia coli and Saccharomyces cerevisiae for secretion of cellulase.

Today, our energy resources mostly depend on petroleum, coal, natural gas, and hydroelectricity. Some renewable energy such as sunlight, wind, rain, tides, and geothermal heal are known as renewable energy source; however, it only covers 19 % of global final energy consumption (2008). We need energy resource that does not depend on fossil fuel. If we can create cellulose degradation system, people can use the most abundant carbon resource in the world with low cost and small energy. This will lead us solve world problems such as energy and food consumption and we hope to create sustainable society. Our BioBrick will save the world!

BioBricks

From BioBrick, we used endo-glucanase, cenA, (BBa_K118023)and exo-glucanase, cex, (BBa_K118022). Also, we used beta-gluctocidase which was miss-registered in BioBrick. Not only for their single use, but also we also wanted these proteins to cooperate each other as CellulaseBrick. Therefore, we originally cloned these genes into silver-standard protein. Furthermore, we coloned several other cellulase for new parts in BioBrick. To improve competency of cellulase, we also cloned cellulose binding module protein (BBa_K392014).

Cellulose Binding Module

New Cellulase Parts

Testing the cellulase

In nature, cellulose exists as insoluble compound. Therefore, in addition to pure cellulose, we used ASC and CMC as substrates to test for cellulase activity. ASC stands for Acid Swollen Cellulose and it pretreated with condensed phosphate. CMC is an abbreviation for carboxymethylcellulose and it is a derivative of cellulose. The structure of CMC is given below; a hydroxyl group is substituted for a carboxy-methyl group: