Visualization of Polyhydroxyalkanoate Accumulated in Waste Activated Sludge

Abstract

Polyhydroxyalkanoates (PHAs) can be produced with municipal waste activated sludge from biological wastewater treatment processes. Methods of selective fluorescent staining with confocal laser scanning microscopy (CLSM) were developed and optimized to evaluate the distribution of PHA storage activity in this mixed culture activated sludge microbial communities. Selective staining methods were applied to a municipal activated sludge during pilot scale PHA accumulation in replicate experiments. Visualization of stained flocs revealed that a significant but limited fraction of the biomass was engaged with PHA accumulation. Accumulated PHA granules were furthermore heterogeneously distributed within and between flocs. These observations suggested that the PHA content for the bacteria storing PHAs was significantly higher than the average PHA content measured for the biomass as a whole. Optimized staining methods provided high acuity for imaging of PHA distribution when compared to other methods reported in the literature. Selective staining methods were sufficient to resolve and distinguish between distinctly different morphotypes in the biomass, and these observations of distinctions have interpreted implications for PHA recovery methods. Visualization tools facilitate meaningful insights for advancements of activated sludge processes where systematic observations, as applied in the present work, can reveal underlying details of structure–function relationships.

A review on microbes mediated resource recovery and bioplastic (polyhydroxyalkanoates) production from wastewater

“… No PHA accumulation was detected in fresh activated sludge. Nile Red has better PHA accumulation signal generation than Nile Blue A 48 ± 2 - [ 172 ] Bacillus pumilus NMG5 strain Paper factories wastewater (Minh Hung paper factory) 30 L Dissolved oxygen 4 mg.L − 1 COD removal was 95.93%. Phosphorus and nitrogen removal efficiencies were 83.55% and 79.36% 42.28 - [ 173 ] Haloferax mediterranei Sesame seed wastewater 5 L Mixing rate 230 rpm, at 37 °C for 4 d, pH 7.0, aeration 0.75 VVM 6 g.L − 1 yeast extract and 100 g.L − 1 NaCl was optimum for PHA accumulation.…”

Exploring the Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Production Potential of Total Petroleum Hydrocarbon Degrading Bacteria Using Oily Sludge Waste as Feedstock

“…Few reports are available indicating the potential of bacteria isolated from oily sludge-contaminated soil for PHA production. , Crude oil is a rich source of various hydrocarbons with highly reduced carbon backbones, which can serve as a source of high energy (42–47 kJ/g). − This amount of energy is much higher than that obtained from proteins (17 kJ/g), carbohydrates (17 kJ/g), or even fats (37 kJ/g). , The unavailability of essential nutrients, such as N, P, and Fe, in oily sludge generally limits the rapid exponential growth of hydrocarbon-degrading microbes. Some of these bacteria can accumulate PHA in such poor nutritional environments as it is useful for their survival under stressful conditions. , In some studies, PHA also been referred to as stress granule. , This becomes the basis for recovering PHA through the bioremediation of oily sludge containing petroleum derived hydrocarbons.…”