An Electro-Microbial Process to Uncouple Food Production from Photosynthesis for Application in Space Exploration.

Here we propose the concept of an electro-microbial route to uncouple food production from photosynthesis, thereby enabling production of nutritious food in space without the need to grow plant-based crops. In the proposed process, carbon dioxide is fixed into ethanol using either chemical catalysis or microbial carbon fixation, and the ethanol created is used as a carbon source for yeast to synthesize food for human or animal consumption. The process depends upon technologies that can utilize electrical energy to fix carbon into ethanol and uses an optimized strain of the yeast Saccharomyces cerevisiae to produce high-quality, food-grade, single-cell protein using ethanol as the sole carbon source in a minimal medium. Crops performing photosynthesis require months to mature and are challenging to grow under the conditions found in space, whereas the electro-microbial process could generate significant quantities of food on demand with potentially high yields and productivities. In this paper we explore the potential to provide yeast-based protein and other nutrients relevant to human dietary needs using only ethanol, urea, phosphate, and inorganic salts as inputs. It should be noted that as well as having potential to provide nutrition in space, this novel approach to food production has many valuable terrestrial applications too. For example, by enabling food production in climatically challenged environments, the electro-microbial process could potentially turn deserts into food bowls. Similarly, surplus electricity generated from large-scale renewable power sources could be used to supplement the human food chain.

Eukaryogenesis: The Rise of an Emergent Superorganism.

Although it is widely taught that all modern life descended via modification from a last universal common ancestor (LUCA), this dominant paradigm is yet to provide a generally accepted explanation for the chasm in design between prokaryotic and eukaryotic cells. Counter to this dominant paradigm, the viral eukaryogenesis (VE) hypothesis proposes that the eukaryotes originated as an emergent superorganism and thus did not evolve from LUCA via descent with incremental modification. According to the VE hypothesis, the eukaryotic nucleus descends from a viral factory, the mitochondrion descends from an enslaved alpha-proteobacteria and the cytoplasm and plasma membrane descend from an archaeal host. A virus initiated the eukaryogenesis process by colonising an archaeal host to create a virocell that had its metabolism reprogrammed to support the viral factory. Subsequently, viral processes facilitated the entry of a bacterium into the archaeal cytoplasm which was also eventually reprogrammed to support the viral factory. As the viral factory increased control of the consortium, the archaeal genome was lost, the bacterial genome was greatly reduced and the viral factory eventually evolved into the nucleus. It is proposed that the interaction between these three simple components generated a superorganism whose emergent properties allowed the evolution of eukaryotic complexity. If the radical tenets of the VE hypothesis are ultimately accepted, current biological paradigms regarding viruses, cell theory, LUCA and the universal Tree of Life (ToL) should be fundamentally altered or completely abandoned.

Evidence supporting a viral origin of the eukaryotic nucleus.

The defining feature of the eukaryotic cell is the possession of a nucleus that uncouples transcription from translation. According to the updated Viral Eukaryogenesis (VE) hypothesis presented here, the eukaryotic nucleus descends from the viral factory of a DNA virus that infected the archaeal ancestor of the eukaryotes. The VE hypothesis implies that many unique features of the nucleus, including the mechanisms by which the eukaryotic nucleus uncouples transcription from translation, should be viral rather than cellular in origin. The modern eukaryotic nucleus uncouples transcription from translation using a complex process employing hundreds of eukaryotic specific genes acting in concert. This intricate process is primed by the eukaryote specific 7-methylguanylate (m7G) cap on eukaryotic mRNA that targets mRNA for splicing, nuclear export, and cytoplasmic translation. It is shown here that homologues of the eukaryotic m7G capping apparatus are present in viruses of the Mimiviridae yet are apparently absent from archaea generally, and specifically from Lokiarchaeota, a proposed archaeal relative of the eukaryotes. Phylogenetic analysis of the m7G capping apparatus shows that eukaryotic nuclei and Mimiviridae obtained this shared pathway from a common ancestral source that predated the origin of the Last Eukaryotic Common Ancestor (LECA). These results are consistent with the hypothesis that the eukaryotic nucleus and the Mimiviridae obtained these abilities from an ancient virus that could be considered the 'First Eukaryotic Nuclear Ancestor' (FENA).

Techno-economic implications of improved high gravity corn mash fermentation.

The performance of Saccharomyces cerevisiae MBG3964, a strain able to tolerate >18% v/v ethanol, was compared to leading industrial ethanol strain, Fermentis Ethanol Red, under high gravity corn mash fermentation conditions. Compared to the industrial ethanol strain, MBG3964 gave increased alcohol yield (140g L(-1) vs. 126g L(-1)), lower residual sugar (4g L(-1) vs. 32g L(-1)), and lower glycerol (11g L(-1) vs. 12g L(-1)). After 72h fermentation, MBG3964 showed about 40% viability, whereas the control yeast was only about 3% viable. Based on modelling, the higher ethanol tolerant yeast could increase the profitability of a corn-ethanol plant and help it remain viable through higher production, lower unit heating requirements and extra throughput. A typical 50M gal y(-1) dry mill ethanol plant that sells dried distiller's grain could potentially increase its profit by nearly $US3.4M y(-1) due solely to the extra yield, and potentially another $US4.1M y(-1) if extra throughput is possible.

Use of population genetics to derive nonrecombinant Saccharomyces cerevisiae strains that grow using xylose as a sole carbon source.

According to scientific dogma, Saccharomyces cerevisiae cannot grow utilizing xylose as a sole carbon source. Although recombinant DNA technology has overcome this deficiency to some degree, efficient utilization of xylose appears to require complex global changes in gene expression. This complexity provides a significant challenge to the development of yeasts suitable for the utilization of xylose-rich lignocellulosic substrates. In contrast to the dogma, we have found that native strains of S. cerevisiae can grow on xylose as a sole carbon source, albeit very slowly. This observation provided the basis for a new approach using natural selection to develop strains of S. cerevisiae with improved ability to utilize xylose. By applying natural selection and breeding over an extended period, we have developed S. cerevisiae strains that can double in less than 6 h using xylose as a sole carbon source. Strains with improved growth rate possessed increased xylose reductase and xylitol dehydrogenase activities, with the latter showing the greater improvement. This unique, completely nonrecombinant approach to developing xylose-utilizing strains of S. cerevisiae opens an alternative route to the development of yeast that can fully utilize lignocellulosic substrates.

The application of PCR for the isolation of a lipase gene from the genomic DNA of an Antarctic microfungus.

We successfully isolated a lipase gene (designated lipPA) directly from the genomic DNA of an Antarctic isolate of Penicillium allii using PCR and a suite of degenerate primers specifically designed to target two conserved regions of fungal lipase genes. We applied the biolistic transformation system to successfully integrate the lipPA gene into a heterologous fungal host, Trichoderma reesei, one of the most powerful secretors of extracellular proteins, and induced the transformant to secrete an active lipase into the growth medium. The recombinant lipase had a temperature optimum of 25 degrees C at pH 7.9 and retained greater than 50% of the maximum activity from 10 degrees C to 35 degrees C and over a pH range from 4.0 to 8.5.

Prospecting for novel lipase genes using PCR.

A PCR method suitable for the isolation of lipase genes directly from environmental DNA is described. The problems associated with the low levels of similarity between lipase genes were overcome by extensive analysis of conserved regions and careful primer design. Using this method, a lipase gene (oli-lipase) was isolated directly from environmental DNA. This lipase showed less than 20% similarity with other known lipases at the amino acid level. The study also revealed that distantly related members of the alpha/beta hydrolase superfamily share similar conserved motifs with the lipases, thus making these genes targets for gene prospecting by PCR.