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Two uncharacterized nicotinamide adenine dinucleotide (NADH) oxidases (named as LpNox1, LpNox2) from Lactobacillus pentosus ATCC 8041 were cloned and overexpressed in Escherichia coli BL21 (DE3). The sequence analysis revealed that the two enzymes are water-forming Noxs with 64 % and 52 % identity to LbNox from Lactobacillus brevis DSM 20054. The optimal pH and temperature of the purified LpNox1 and LpNox2 were 7.0 and 8.0 and 35 and 40 °C, respectively, with K M of 99.0 μM (LpNox1) and 27.6 μM (LpNox2), and yielding catalytic efficiency k cat/K M of 1.0 and 0.2 μM(-1) s(-1), respectively. Heat inactivation studies revealed that the two enzymes are relatively instable. The application of LpNox1 for the regeneration of NAD(+) was demonstrated by coupling with a glycerol dehydrogenase-catalyzed oxidation of glycerol to 1,3-dihydroxyacetone. The characteristics of the LpNox1 could prove to be of interest in industrial application such as NAD(+) regeneration in dehydrogenase-catalyzed oxidations.

The behavior of clogging has a close relationship with the biofilm attached on inner surface of the pipeline in a drip irrigation system using reclaimed water. Therefore, inhibiting biofilm growth is the key to completely addressing the clogging problem. Water shear forces play a vital role in the formation, development and detachment of biofilm. In order to find out the accumulation mechanism of biofilm under different water shear forces, this paper considered 8 different shear forces with a range of [0, 0.7]Pa on the inner surface of pipelines in drip irrigation systems using three kinds of reclaimed water. The results indicate that dry weight (DW), phospholipid fatty acids (PLFAs) and extracellular polymeric substance (EPS) of biofilms show a S-type trend, the maximum contents were observed when τ was 0.2 Pa or 0. 35 Pa. Besides, the influence of water shear forces on biofilms is dual. The formation of biofilm is a dynamic stabilization process. When there is a relatively large shear force, it is favorable to the transport and renewal of microorganisms and nutrients. Meantime, the renewal speed of biofilms is also relatively fast. It is easy to form the biofilms with large surface and small thickness due to relatively high possibility of detachment. When the shear force is small, the transport speed of microorganisms and nutrients are limited, and the ability of microorganisms to secrete polysaccharides is reduced, which makes the nutrients needed for microbial growth insufficient and the adhesion between particles is also reduced, resulting in loose, unstable and an easily removed biofilm structure. After a comprehensive consideration of the dual influence, the critical controlling threshold of internal water shear force was obtained as [0, 0.20] ∪ [0.35, +∞] Pa. In addition, the growth model established in this paper can well describe the growth kinetics of attached biofilms, and provide theoretical reference for monitoring the occurrence of bio-clogging process in drip irrigation systems. Drip irrigation is considered to be the safest and most reliable irrigation method for reclaimed water because of its precision and controllability. However, the reclaimed water still contains a large amount of particulate matter, microorganisms, organic matter, nitrogen and phosphorus, which greatly increases the risk of clogging in drip irrigation systems 1. A large number of studies have found that when using reclaimed water, the clogging of drip irrigation systems has a close relationship with the formation and growth of biofilms attached on inner walls of the pipeline 2-5. A common form of clogging in drip irrigation systems is that after being formed in the pipeline system, especially on inner walls of drip irrigation pipelines, the biofilms fall into the drip irrigation emitter and this results in clogging. Multiple studies have shown that the clogging is a difficult problem to solve 3-7. At present, the problem of clogging in drip irrigation systems can be solved to some extent by properly setting up filtration equ...

The disadvantage of the expensive consumption of NAD(+) for the production of DHA has been overcome.