Energy metabolism response of Litopenaeus vannamei to combined stress of acute cold exposure and waterless duration: Implications for physiological regulation and waterless live transport.

Maintaining the homeostasis of energy metabolism is crucial for organism's stress tolerance and survival. Acute cold exposure (AC) and waterless duration (WD) represent the two predominate abiotic stressors during waterless live transport of Litopenaeus vannamei. Although previous reports have explored the physiological response of L. vannamei to combined stress AC + WD, the roles of energy metabolism response in regulation of stress tolerance remains unknown. The present study comparatively examined the variations of energy metabolism-related indicators in hemolymph (cortisol, hemocyanin, glucose and lactate), hepatopancreas and muscle tissues (levels of lactate and glycogen, activities of hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH) and adenosine triphosphatase (ATPase), and ATP levels). Combined stress significantly disturbed the homeostasis of energy metabolism with the increase in levels of hemocyanin, glucose and lactate, and decrease in glycogen and ATP content (P < 0.05). In addition, the activities of HK, PFK, PK, and SDH initially elevated and then decreased with the prolongation of combined stress from 3h to 9h duration, while the activity of lactate dehydrogenase (LDH) remained gradual elevation and ATPase activity decreased in a duration time dependent manner throughout the experiment. These alterations revealed that exposure to combined stress could accelerate anaerobic metabolism at initial stage and inhibit aerobic metabolism in a duration time-dependent manner, following with the reduction of energy biosynthesis and the disturbance of energy metabolism equilibrium. On the other hand, the progressive impairment on hepatopancreas tissue was observed under combined stress. In summary, the deficiency of ATP supply and histopathological injures on hepatopancreas tissue might the underlying mechanisms inducing mortality of L. vannamei during live transport.

The efficient biomineralization and adsorption of cadmium (Cd2+) using secretory organo-biominerals (SOBs) produced by screened Alcaligenes faecalis K2.

Cadmium-contaminated wastewater has attracted increasing concerns due to its non-biodegradable properties and high toxicity. To explore eco-friendly and economically feasible strategies, the screened Alcaligenes faecalis K2 were employed for the biomineralization and recovery of Cd2+ from wastewater while producing considerable secretory organo-biominerals (SOBs) as bioadsorbents. At 75 mg/L Cd2+ exposure, 85.5% of Cd2+ was removed by K2, 43.0% of which was fixed in the granular SOBs. SOBs were convenient for separating from the solution. The adsorption capacity of granular sorbent made from SOBs was verified to be greater than 77.1 mg/g. Practically, 89.5% of 75 mg/L of Cd2+ could be stably removed while ereK2 continuously generated SOBs in a moving-bed biofilm reactor (MBBR). To sum up, the production of bioadsorbents can be achieved by K2, while removing Cd with live microorganisms, which was conducive to making full use of materials and improving Cd removal efficiency.