Free ammonia offers algal crop protection from predators in dairy wastewater and ammonium-rich media

Abstract

Cost-effective methods for protecting crops from grazing organisms like rotifers are needed to reduce the risk of pond crashes in mass algal cultures. We present a novel strategy to optimize the exposure time to free ammonia, via control of media pH, in both defined media and dairy anaerobic digester effluent to suppress rotifers and maintain algal productivity. We tested five different free ammonia exposure times (0, 1, 2, 6, and 12h) and found a significant nonlinear effect of exposure time (p<0.0001) but not pH (p>0.9) on rotifer survival. In both media types, 6-12h of elevated free ammonia significantly reduced Brachionus plicatilis rotifer survival with no negative effects on Nannochloropsis oculata, while shorter exposure times were insufficient to inhibit rotifers, leading to severe algal culture crashes. These results suggest that algal crops can be protected from rotifers, without productivity loss, by elevating free ammonia for 6 or more hours.

Application of biosurfactant from Bacillus subtilis C9 for controlling cladoceran grazers in algal cultivation systems

“…In addition to the recovered C9-biosurfactant, HPLC-grade surfactin from B. subtilis (Sigma-Aldrich, St. Louis, MO, USA) was tested under identical experimental conditions at four concentrations (0, 6, 20, and 60 mg/L) in plain COMBO medium to confirm whether the main surfactant compound of C9-biosurfactant is primarily contributing to its cladoceran control activity 34 , 35 . All experiments were performed in a temperature-controlled room at 25 ± 1 °C under the light intensity of 150 µmol·m −2 ·s −1 , and the pH level of each tube culture ranged between 7.0 and 8.0 throughout the experimental period, ensuring no significant influence of ammonia toxicity on the mortality of algal grazers 74 .…”

Microalgae and Clean Technologies: A Review

“…Algae are more productive than other terrestrial biofuel crops because they may present a better oil yield, and bioproducts from microalgae exhibit considerable potential in many fields. In this context, research on crop protection has been increasing in recent years because there are grazing pests (e.g., rotifers, ciliates, and cladocerans) and pathogens (e.g., bacteria, viruses, and fungi) that could interfere with the production of microalgal biomass and bioproducts …”

“…The development of methods for crop protection is essential to inhibit pests without affecting microalgae and to increase the commercialization of bioproducts from these microorganisms on an industrial scale. Some of the promising crop protection agents for sustainable algaculture are related, such as ammonia, copper, rotenone, hypochlorite, and quinine . According to El‐Sayed et al., rotenone can be used as a crop protector for algae because it is preventative against grazing predators, avoids algal open pond crashes, presents a low cost, and stimulates the algal biofuel industry.…”

“…According to El‐Sayed et al., rotenone can be used as a crop protector for algae because it is preventative against grazing predators, avoids algal open pond crashes, presents a low cost, and stimulates the algal biofuel industry. Thomas et al . studied the effects of free ammonia as an algal crop protector in defined media and dairy wastewater in the presence of Brachionus plicatilis rotifers.…”

Modeling the impact of rotifer contamination on microalgal production in open pond, photobioreactor and thin layer cultivation systems

“…Many solutions have been proposed in the literature, ranging from chemical (e.g. rotenone [23], free NH 3 [24], toosendanin [25], CO 2 asphyxiation [26]), mechanical (e.g. filtration [27]), physical (e.g.…”