Silica sol-gel encapsulation of cyanobacteria: lessons for academic and applied research.

Cyanobacteria inhabit nearly every ecosystem on earth, play a vital role in nutrient cycling, and are useful as model organisms for fundamental research in photosynthesis and carbon and nitrogen fixation. In addition, they are important for several established biotechnologies for producing food additives, nutritional and pharmaceutical compounds, and pigments, as well as emerging biotechnologies for biofuels and other products. Encapsulation of living cyanobacteria into a porous silica gel matrix is a recent approach that may dramatically improve the efficiency of certain production processes by retaining the biomass within the reactor and modifying cellular metabolism in helpful ways.

Diffusion of dissolved ions from wet silica sol-gel monoliths: implications for biological encapsulation.

Divalent nickel (Ni(2+)), Cu(II)EDTA, methyl orange, and dichromate were used to investigate diffusion from hydrated silica sol-gel monoliths. The objective was to examine diffusion of compounds on a size regime relevant to supporting biological components encapsulated within silica gel prepared in a biologically compatible process space with no post-gelation treatments. With an initial sample set, gels prepared from tetraethoxysilane were explored in a factorial design with Ni(2+) as the tracer, varying water content during hydrolysis, acid catalyst present during hydrolysis, and the final concentration of silica.

Transcriptomic responses of Synechocystis sp. PCC 6803 encapsulated in silica gel.

Global gene expression of Synechocystis sp. PCC 6803 encapsulated in silica gel was examined by microarray analysis. Cultures were encapsulated in gels derived from aqueous precursors or from alkoxide precursors and incubated under constant light for 24 h prior to RNA extraction.

Photosynthetic accumulation of carbon storage compounds under CO₂ enrichment by the thermophilic cyanobacterium Thermosynechococcus elongatus.

The growth characteristics of Thermosynechococcus elongatus on elevated CO₂ were studied in a photobioreactor. Cultures were able to grow on up to 20% CO₂. The maximum productivity and CO₂ fixation rates were 0.

Evaluation of encapsulation stress and the effect of additives on viability and photosynthetic activity of Synechocystis sp. PCC 6803 encapsulated in silica gel.

Stresses imposed on the cyanobacterium Synechocystis sp. PCC 6803 by various compounds present during silica sol-gel encapsulation, including salt, ethanol (EtOH), polyethylene glycol (PEG), glycerol, and glycine betaine, were investigated. Viability of encapsulated cells and photosynthetic activity of cells stressed by immediate (2 min) and 24-h exposure to the five stress-inducing compounds were monitored by pulse amplitude modulated fluorometry.

Effects of selected electron transport chain inhibitors on 24-h hydrogen production by Synechocystis sp. PCC 6803.

One factor limiting biosolar hydrogen (H(2)) production from cyanobacteria is electron availability to the hydrogenase enzyme. In order to optimize 24-h H(2) production this study used Response Surface Methodology and Q2, an optimization algorithm, to investigate the effects of five inhibitors of the photosynthetic and respiratory electron transport chains of Synechocystis sp. PCC 6803.

Optimization of pH and nitrogen for enhanced hydrogen production by Synechocystis sp. PCC 6803 via statistical and machine learning methods.

The nitrogen (N) concentration and pH of culture media were optimized for increased fermentative hydrogen (H(2)) production from the cyanobacterium, Synechocystis sp. PCC 6803. The optimization was conducted using two procedures, response surface methodology (RSM), which is commonly used, and a memory-based machine learning algorithm, Q2, which has not been used previously in biotechnology applications.

Whole-genome transcriptional and physiological responses of Nitrosomonas europaea to cyanide: identification of cyanide stress response genes.

Nitrosomonas europaea (ATCC 19718) is one of several nitrifying species that participate in the biological removal of nitrogen from wastewater by oxidizing ammonia to nitrite, the first step in nitrification. Because nitrification is quite sensitive to cyanide, a compound often encountered in wastewater treatment plants, we characterized the physiological and transcriptional responses of N. europaea cells to cyanide.

Thermotolerant hydrogenases: biological diversity, properties, and biotechnological applications.

Hydrogenases are metalloproteins that catalyze the oxidation and reduction of molecular hydrogen and play a crucial role in many microbial metabolic processes. A subset of hydrogenases capable of functioning at temperatures from 50 to 125 degrees C is found in thermophilic microorganisms. Most known thermotolerant hydrogenases contain a [NiFe] active site and are either bidirectional or uptake type.

Candidate stress genes of Nitrosomonas europaea for monitoring inhibition of nitrification by heavy metals.

Heavy metals have been shown to be strong inhibitors of nitrification in wastewater treatment plants. In this research, the effects of cadmium, copper, and mercury on Nitrosomonas europaea were studied in quasi-steady-state batch reactors. When cells were exposed to 1 microM CdCl2, 6 microM HgCl2, or 8 microM CuCl2, ammonia oxidation rates were decreased by about 90%.

High-throughput screening assay for biological hydrogen production.

This paper describes a screening assay, compatible with high-throughput bioprospecting or molecular biology methods, for assessing biological hydrogen (H2) production. While the assay is adaptable to various physical configurations, we describe its use in a 96-well, microtiter plate format with a lower plate containing H2-producing cyanobacteria strains and controls and an upper, membrane-bottom plate containing a color indicator and a catalyst. H2 produced by cells in the lower plate diffuses through the membrane into the upper plate, causing a color change that can be quantified with a microplate reader.

Genome-wide transcriptional responses of Nitrosomonas europaea to zinc.

Nitrosomonas europaea, a Gram-negative obligate chemolithoautotroph, participates in global nitrogen cycling by carrying out nitrification and derives energy for growth through oxidation of ammonia. In this work, the physiological, proteomic, and transcriptional responses of N. europaea to zinc stress were studied.