No abstract

CONSPECTUS:Water security to protect human lives and support sustainable development is one of the greatest global challenges of this century. While a myriad of water pollutants can impact public health, the greatest threat arises from pathogenic bacteria that can be harbored in different components of water treatment, distribution, and reuse systems. Bacterial biofilms can also promote water infrastructure corrosion and biofouling, which substantially increase the cost and complexity of many critical operations. Conventional disinfection and microbial control approaches are often insufficient to keep up with the increasing complexity and renewed relevance of this pressing challenge. For example, common disinfectants cannot easily penetrate and eradicate biofilms, and are also relatively ineffective against resistant microorganisms. The use of chemical disinfectants is also curtailed by regulations aimed at minimizing the formation of harmful disinfection byproducts. Furthermore, disinfectants cannot be used to kill problematic bacteria in biological treatment processes without upsetting system performance. This underscores the need for novel, more precise, and more sustainable microbial control technologies. Bacteriophages (phages), which are viruses that exclusively infect bacteria, are the most abundant (and perhaps the most underutilized) biological resource on Earth, and hold great promise for targeting problematic bacteria. Although phages should not replace broad-spectrum disinfectants in drinking water treatment, they offer great potential for applications where selective targeting of problematic bacteria is warranted and antimicrobial chemicals are either relatively ineffective or their use would result in unintended detrimental consequences. Promising applications for phage-based biocontrol include selectively suppressing bulking and foaming bacteria that hinder activated sludge clarification, mitigating proliferation of antibiotic resistant strains in biological wastewater treatment systems where broad-spectrum antimicrobials would impair pollutant biodegradation, and complementing biofilm eradication efforts to delay corrosion and biofouling. Phages could also mitigate harmful cyanobacteria blooms that produce toxins in source waters, and could also serve as substitutes for the prophylactic use of antibiotics and biocides in animal agriculture to reduce their discharge to source waters and the associated selective pressure for resistant bacteria. Here, we consider the phage life cycle and its implications for bacterial control, and elaborate on the biochemical basis of such potential application niches in the water supply and reuse cycle. We also discuss potential technological barriers for phage-based bacterial control and suggest strategies and research needs to overcome them.

Fermentation of food waste to l-lactic acid (l-LA), a high value-added platform molecule, is a green approach for resource recovery. However, low yield and optical activity (OA) of l-LA are key limiting factors for such efforts. Here, we report that ammonium addition (300 mg of NH4 +-N/L) can double the yield of LA and increase OA of l-LA by fivefold during repeated batch fermentation of food waste. This coincided with a threefold increase in the glycolysis activity and an increase in the relative abundance of key lactic acid bacteria (LAB) genera and the ldhL gene associated with l-LA production. Ammonium addition provided essential nitrogen for LAB growth (47% of 15NH4 +-N underwent assimilation versus 15% oxidized to 15NO3 –-N and 31% to 29N2 and 30N2) and resulted in a stable reducing environment (the oxidation–reduction potential, ORP, ranged from −470 to −320 mV) that favors the reduction of pyruvate to l-lactate. Specifically, the added ammonium promoted beneficial population and metabolic shifts, including an increase in intracellular NADH levels (0.46 ± 0.02 vs 0.26 ± 0.01 mM for unamended controls) that significantly increased the l-LA yield. Overall, this study provides a practical way to enhance l-LA production with high OA during food waste fermentation and highlights ammonium as an overlooked biostimulator for food waste biorefinery.

The combined experimental and computational study demonstrates an inverse relationship between phage-nanocomposite conjugate (PNC) size and biofilm eradication potential.