Conversion of proteins into biofuels by engineering nitrogen flux

Abstract

Biofuels are currently produced from carbohydrates and lipids in feedstock. Proteins, in contrast, have not been used to synthesize fuels because of the difficulties of deaminating protein hydrolysates. Here we apply metabolic engineering to generate Escherichia coli that can deaminate protein hydrolysates, enabling the cells to convert proteins to C4 and C5 alcohols at 56% of the theoretical yield. We accomplish this by introducing three exogenous transamination and deamination cycles, which provide an irreversible metabolic force that drives deamination reactions to completion. We show that Saccharomyces cerevisiae, E. coli, Bacillus subtilis and microalgae can be used as protein sources, producing up to 4,035 mg/l of alcohols from biomass containing ∼22 g/l of amino acids. These results show the feasibility of using proteins for biorefineries, for which high-protein microalgae could be used as a feedstock with a possibility of maximizing algal growth and total CO(2) fixation.

Effect of Silica on Carbohydrate Content of Mixed Culture Phaeodactylum sp. and Chlorella sp

“…The efficiency of light becomes a major limiting factor in large-scale cultivation and outdoor. High light intensity in the raceway pond causing a high rate of photosynthesis and the availability of N high in the medium causes the protein synthesis to be higher, so that the carbohydrate content in dry weight being low 30 . Ethanol produced by fermentation in batch and fed batch using Saccharomyces microbes and can produce high ethanol, about 12-14%.…”

Physiological Effects of GLT1 Modulation in Saccharomyces cerevisiae Strains Growing on Different Nitrogen Sources

“…This yeast is able to metabolize a wide variety of nitrogen sources via enzymatic reactions that are indirectly linked in a network of physiological responses. These responses and their regulations are crucial to the yeast for optimizing the exploitation of the environment and are therefore crucial to improve the biotransformation of protein-rich raw materials, such as whey or exhausted biomasses derived from fermentation processes [1,17]. Indeed, the replacement of petrochemistry-based transport fuels and bulk chemicals by yeast industrial biotechnology requires cost-effective fermentation processes, where yields of substrate conversion into product must approach the maximal theoretical values.…”

Utilization of Microalgal Biofractions for Bioethanol, Higher Alcohols, and Biodiesel Production: A Review

“…Microalgae (such as Chlorella sp., Scenedesmus sp., and Chlamydomonas sp.) have an abundance of carbohydrates (cellulose) and proteins that can be converted to bioalcohol under specific fermentation conditions [44][45][46]. Biomass pretreatment enhances the hydrolysis rate of substrate as it enhances the solubility of sugar, increases surface area, improves the digestibility of substrate by weakening the cell wall, making enzymes more accessible [47].…”