Production of bacterial chitosan-like bioflocculant (BF) and its application for the pretreatment for making drinking water using RO-membrane water supplier machines

Shiew Wei Lau
Curtin University, Sarawak, Malaysia

I am Dr. Shiew Wei Lau, Lecturer, Dept. of Chemical Engineering, Curtin Univ., Sarawak (Malaysia). I have a collaborative research with Dr. Takeo, Associate Prof., Dept. of Applied Chemistry, Univ. of Hyogo. This research focuses on the production of bacterial chitosan-like bioflocculant (BF) for the pretreatment of drinking-water production using portable Reverse Osmosis (RO) membrane machines, which contribute to water supply in emergencies and disasters. RO membranes are weak against fouling by suspended solids in raw water. The best way to remove suspended solids from raw water safely is to use non-toxic BFs for the pretreatment. Citrobacter strains can produce a chitosan-like BF from acetate. To produce a large amount of the BF, it is very important to know the BF biosynthetic pathway and the mechanisms of the polymerization and secretion of the BF in the BF-producing strains.
During my stay, at first, I learnt how to treat bacterial cells (ex. preparation of medium and cultivation for the bacterial strains) in the first two weeks, and then, I learnt how to disrupt genes to determine the BF biosynthetic pathway and to improve the BF production. The target genes were involved in the production of UDP-N-acetylglucosamine, which is expected to be a direct precursor for the polymerization of the BF. I carried out experiments to make DNA fragments by PCR for the gene disruption and I successfully got the expected DNA fragments by the experiment. This is my first experience dealing with genetic engineering experiments. The DNA fragments would be used for gene disruption by my colleagues in Univ. of Hyogo later. Another purpose for this stay is to experience the BF production in flasks and the BF concentration with hollow fiber membrane modules. For the purpose, I needed to treat large amounts of bacterial cultures. However, I am now pregnant and am not advisable to touch the bacterial cells directly or take up aerosol including bacterial cells. Thus, I observed the processes carried out by the members of Dr. Takeo’s lab. Meanwhile, I introduced my work on the dewatering of digested sludge using the commercially available chitosan from Sigma and the BF from Citrobacter youngae GTC01314 prepared in Dr. Takeo’s lab in the seminar (19th, Jun.). Several researchers of Univ. of Hyogo and many master course students kindly joined the seminar and we had a good discussion in the seminar. In addition, Dr. Takeo took me to Osaka Univ. to have academic communication with Prof. Michihiko Ike and his lab. members on 20th, June. I showed the above-mentioned work for the members (photo, 20th, Jun.). Assistant Prof. Masashi Kuroda kindly introduced Prof. Ike’s lab facilities and I had a good time there.
For the contribution to Univ. of Hyogo, I provided a scientific English lecture on climate change for many undergraduate students of Dept. of Applied Chemistry and Chemical Engineering and Dept. of Mechanical Engineering and Metallurgy (13th, Jun.).
During this stay, as I could learn how to prepare the BF of Citrobacter strains and how to improve the production, I would like to produce the BF in my lab. in future and to use the BF for the dewatering and flocculation experiments through the collaboration with Dr. Takeo. At last, I would like to acknowledge Hyogo Earthquake Memorial 21st Century Research Institute for providing this good opportunity (Hyogo Overseas Research Network (HORN) fellowship).