Such cells cannot be counted under standard aerobic conditions, but can be cultured under conditions where reactive oxygen species are neutralised (ROS-neutralised

conditions), e.g., in growth medium supplemented with the peroxide scavenger sodium pyruvate and incubated under anaerobic conditions to prevent cellular respiration [8, 11]. The significance of this was shown in our recent study using a solar photocatalytic reactor under different flow rates with low sunlight and high flow rates showing substantial sub-lethal injury BTK inhibitor of A. hydrophila[12]. pH is a major variable in aquaculture systems; it influences the survival and growth of fish in culture and affects the physiological condition of the end product [13]. Lower pH generally decreases the survival and reproductive maturity of fish, while high pH can cause toxic ammonia imbalance within an aquaculture system [6]. The acceptable pH range for water used in aquaculture production is typically from 6.5 to 9 [14]. In solar photocatalysis, pH is also one of the main variables affecting the process. At higher pH levels, TiO2 surfaces

are negatively charged and repulse anionic compounds in water [15]. In contrast, at low pH the density of positively charged catalyst increases which can then form an electrostatic link with the negatively charged surfaces of bacteria, resulting in a higher rate of microbial photo-disinfection [16]. Herrera Melian and his co-workers showed higher bacterial inactivation at pH 5 than at pH 7.8 which is consistent with such proposals [17]. However, Rincon and DMXAA Pulgarin did not find any differences in bacterial inactivation at pH 4–9 [18]. Consequently, this research investigated microbial inactivation at pH levels of 5, 7 and 9 using the TFFBR system, thereby covering the MRT67307 typical pH range of aquaculture systems [14]. The salinity of aquaculture pond water is an influential factor for fish survival and growth [13]. Selven and Philip stated that salinity can cause negative effects in aquaculture species, linked to the growth and production of toxins by pathogens [19]. They showed that salinity variation increased the virulence

characteristics of Vibrio harveyi in aquaculture systems, reducing the immune response in the shrimp hosts and causing heavy mortality. Wang and Chen showed that 2.5% NaCl significantly increased Carnitine palmitoyltransferase II the growth rate of Photobacterium spp. and that addition of the same amount of NaCl to the growth medium (Tripticase soy broth) also increased the virulence of this pathogen towards shrimps [20]. Seawater has a typical salinity of 3.5% [21]. Therefore, this study investigates the effect of salinity (with and without NaCl and sea salt at 3.5%) on the photocatalytic inactivation of A.hydrophila through the TFFBR system. Imbalance in an aquaculture pond ecosystems can change the water transparency, due to additional suspended solids [22].