Publications

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Algae ponds used in industrial biomass production are susceptible to pathogen or grazer infestation, resulting in pond crashes with high economic costs. Current methods to monitor and mitigate unhealthy ponds are hindered by a lack of early indicators that precede culture crash. We used solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to identify volatiles emitted from healthy and rotifer infested cultures of Microchloropsis salina. After 48 hours of algal growth, marine rotifers, Brachionus plicatilis, were added to the algae cultures and volatile organic compounds (VOC) were sampled from the headspace using SPME fibers. A GC-MS approach was used in an untargeted analysis of VOCs, followed by preliminary identification. The addition of B. plicatilis to healthy cultures of M. salina resulted in decreased algal cell numbers, relative to uninfected controls, and generated trans-β-ionone and β-cyclocitral, which were attributed to carotenoid degradation. The abundances of the carotenoid-derived VOCs increased with rotifer consumption of algae. Our results indicate that specific VOCs released by infected algae cultures may be early indicators for impending pond crashes, providing a useful tool to monitor algal biomass production and pond crash prevention.

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Open algal ponds are likely to succumb to unpredictable, devastating crashes by one or several deleterious species. Developing methodology to mitigate or prevent pond crashes will increase algal biomass production, drive down costs for algae farmers, and reduce the risk involved with algae cultivation, making it more favorable for investment by entrepreneurs and biotechnology companies. Here, we show that specific algal-bacterial co-cultures grown with the green alga Microchloropsis salina prevented grazing by the marine rotifer, Brachionus plicatilis. We obtained seven algal-bacterial co-cultures from crashed rotifer cultures, maintained them in co-culture with Microchloropsis salina, and used a microalgal survival assay to determine that algae present in each co-culture were protected from rotifer grazing and culture crash. After months of routinely diluting and maintaining these seven algal-bacterial co-cultures, we repeated the assay and found the opposite result: none of the seven bacterial communities protected the microalgae from rotifer grazing. We performed 16S rRNA gene amplicon sequencing on the protective and nonprotective co-culture samples and identified substantial differences in the makeup of the bacterial communities. Protective bacterial communities consisted primarily of Alphaproteobacteria (Rhodobacteraceae) and Gammaproteobacteria (Marinobacter, Pseudomonas, Methylophaga) while nonprotective bacterial communities were less diverse and missing many putatively crucial members. We compared the seven protective communities with the seven nonprotective communities and we correlated specific bacterial amplicon sequence variants with algal protection. With these data, our future work will aim to define and develop an engineered-microbiome that can stabilize industrial Microchloropsis salina cultures by protecting against grazer-induced pond crashes.

Algal biomass is a proposed feedstock for sustainable production of petroleum displacing commodities. However, production of 10% of US demand for liquid transportation fuel from algae would require a 60–150% increase over current agricultural demand for phosphorus fertilizers. Without efforts to recycle major nutrients, algal biomass production can be expected to catalyze a food versus fuel crisis. We have developed a novel and simple process for efficient liberation of phosphate from algal biomass and have demonstrated recycling at both laboratory and pilot scale, of up to 70% of total cellular phosphate from osmotically-shocked but non-denatured Microchloropsis salina biomass using a range of mild incubation conditions. The phosphate released in this process is bioavailable, can support the same level of algal growth as standard nutrients, and does not contain any growth inhibitory compounds as evidenced by its ability to support multiple sequential cycles of growth and remineralization.

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The following trade study was done to answer the following task from the Sandia JPL Collaboration for Europa Lander Statement of Work: Perform a trade study to assess the feasibility of other sterilization/decontamination methods for reducing forward biological contamination on S/C and assess their suitability for PP applications