John N. Wardell

New approach to produce water free of bacteria, viruses, and halogens in a recyclable system.

ABSTRACT The antimicrobial activity of a new cross-linked N-halamine polymer against bacteria and viruses was evaluated. The polymer achieved a 9-log10 reduction of bacteria (both Escherichia coli and Staphylococcus aureus) in 1.5 h and a 5-log10 reduction of bacteriophage PRD1 in 3 h. At the same time, the ability of the nonhalogenated polymer to trap halide ions was examined. The polymer was incorporated into a multifiltration system to study the ability to produce water free of bacteria, viruses, and halide ions. The antimicrobial activity, useful lifetime, halide ion level, and recycling possibilities of the system were quantified on a laboratory scale. A design for a large-scale multifiltration system based on this polymer is proposed.

Kinetics and manipulation of hyphal breakage and its effect on antibiotic production

Erythromycin production in 1.5 l continuous cultures of Saccharopolyspora erythraea, was correlated with the mean mycelial fragment size, which was influenced by culture agitation (750–1 500 rev./min marine/disk turbine impellors). Kinetic parameters for hyphal breakage were determined, and revealed that more highly branched mycelial fragments (hyphal growth unit ∼14 μm, compared to ∼21 μm) were more resistant to breakage. Branching rate depended on growth rate, the more highly branched mycelium being observed at the higher dilution rate. The breakage rate was inversely related to the mycelial fragment diameter at all dilution rates. Manipulating the size distribution of mycelial fragment by using an ultrasonic filter improved specific antibiotic productivity by 33%.

Straw N-halamines: evaluation in single and multistage filtration systems.

New N-halamines (I-Cl and II-Cl) based on cellulose extracted from rice straw have been evaluated in single and multistage filtration systems against bacteria and viruses. Escherichia coli and Staphylococcus aureus were used as examples of Gram-negative and Gram-positive bacteria respectively while PRD1 bacteriophage was used as an example for viruses. II-Cl has achieved 9 log reductions in viable counts against E. coli in 2 h and S. aureus in 1h while it has achieved 7 log reductions against PRD1 in 5 h. The particle size of prepared materials was modified as well as the flow rate through the filtration systems. The antimicrobial activity of modified cellulose was proved to be comparable to some synthetic biocidal polymers from the same type in similar water treatment systems.