Evaluation of growth, nutrient utilization and production of bioproducts by a wastewater-isolated microalga.

Treatment of wastewater while producing microalgal biomass is receiving ever-increasing attention, particularly in the biofuels arena. In this study, a wastewater chlorophyte isolate, Kirchneriella sp., was tested for its ability to be mass cultivated, utilize nutrients from defined media and wastewater, and produce bioproducts of commercial interest. Growth studies were carried out in various systems at scales up to 60L, with Kirchneriella sp. showing an excellent amenability to being cultured. Biomass concentrations of greater than 1gL(-1) were consistently achieved, nitrogen and phosphorus uptake was rapid, and stable medium-term cultures were maintained. Nitrogen limitation affected biomass yield, fatty acid methyl ester (FAME) yield, and cetane index. In contrast, a low phosphorus condition had no effect. Kirchneriella sp. showed an ability to produce several products of commercial value, including carbohydrate-rich biomass, FAME/biodiesel and the pigments ß,ß-carotene and lutein.

Potential alteration of U37K' paleothermometer due to selective degradation of alkenones by marine bacteria isolated from the haptophyte Emiliania huxleyi.

The unsaturation ratio of C(37) alkenones (U(37)(K')) produced by haptophyte microalgae such as Emiliania huxleyi is often used as proxy for past sea surface temperature. In this study, 29 bacterial strains were isolated from cultures of the strain E. huxleyi TWP1. Among alkenone-degrading isolates, the strain Dietzia maris sp. S1 appeared to be able to selectively degrade alkenones leading to increases in the palaeoenvironmental proxy U(37)(K') by +0.05 to +0.10 units, which is equivalent to the change seen when the growth temperature is increased by 1.5-3.0 degrees C. This degradation was shown to involve initial epoxidation of the alkenone double bonds presumably by a monooxygenase, which showed a preference for oxidation of the omega29 double bond. Inconsistencies observed in previous studies of the aerobic microbial degradation of alkenones may simply reflect which species of bacteria were present. Our results confirm that intense aerobic bacterial degradative processes can introduce a bias in palaeotemperature reconstructions especially when there is evidence of substantial aerobic bacterial degradation of the deposited organic matter. The widespread occurrence of epoxyalkenones in the marine environment strongly suggests that selective aerobic bacterial degradation could be major source of uncertainty for palaeotemperature estimation.