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Biological Pathways for the Production of Levulinic Acid from Lignocellulosic Resources
Published in Jitendra Kumar Saini, Surender Singh, Lata Nain, Sustainable Microbial Technologies for Valorization of Agro-Industrial Wastes, 2023
Laura G. Covinich, María Cristina Area
There are a group of microorganisms that were metabolically engineered to produce keto acids. Among the bacteria mostly used to produce keto acids are Escherichia coli (for pyruvic acid) (Hossain et al. 2016), α-Ketoisovaleric acid (Li et al. 2017), levulinic acid (Cheong, Clomburg, and Gonzalez 2016), Pseudomonas aeruginosa (for 2-Keto-D-gluconic acid) (Chia, Van Nguyen, and Choi 2008), Proteus vulgaris (for phenylpyruvic acid) (Coban et al. 2016), Pseudomonas fluorescens (for ketoglutaric acid) (Otto, Yovkova, and Barth 2011), Corynebacterium glutamicum (for α-ketoisovaleric acid) (Buchholz et al. 2013), 5-aminolevulinic acid (Ramzi et al. 2015), α-Ketoisocaproic acid (Bückle-Vallant et al. 2014), ketoglutaric acids (Brüsseler et al. 2019), and Streptomyces cinnamonensis (for α-ketoisovaleric acid) (Pospíšil, Kopecký, and Přikrylová 1998), among others. Among yeast mostly used to produce keto acids are Candida glabrata (for pyruvic acid) (S. Yang et al. 2014), Saccharomyces cerevisiae (for pyruvic acid) (Van Maris et al. 2004), and Yarrowia lipolytica (for ketoglutaric acid) (Guo et al. 2014), among others.
Review on the synthesis, performance and trends of butanol: a cleaner fuel additive for gasoline
Published in International Journal of Ambient Energy, 2022
Genetic modifications of some organisms have improved their biobutanol production potential. Klebsiella pneumonia, a well-known glycerol fermenting microorganism, was engineered to produce 1-butanol. The 1-butanol titre and specific butanol yield reported were 15.03 mg L−1 and 27.79 mg butanol per g cell (Wang, Fan, and Tan 2014). Escherichia coli strain has been used for production of 1-butanol and 1-propanol via the keto-acid intermediates found in microorganism’s native amino acid pathways. The final strain demonstrated a production titre of 2 g/L with nearly 1:1 ratio of butanol and propanol (Shen and Liao 2008). Certain fungi like Saccharomyces cerevisiae have been modified with an n-butanol biosynthetic pathway. Here isozymes from different organisms (S. cerevisiae, E. coli, Clostridium beijerinckii and Ralstonia eutropha) were substituted for the clostridial enzymes and a drastic increase in the butanol production (to 2.5 mg L−1) was observed (Steen et al. 2008). Certain cyanobacteria have been used for butanol production. Cyanobacteria Synechococcus elongatus PCC7942 through artificially engineered ATP consumption pathway modification enabled direct photosynthetic production of 1-butanol (Lan and Liao 2012). Butanol production has been demonstrated in a hyperthermophilic archaeon microbe using an artificial pathway. Acetyl-CoA has been converted to 1-butanol from genes obtained from three different sources. Conversion of glucose to 1- butanol has been demonstrated near 70°C in a microorganism that grows optimally near 100°C (Keller et al. 2015).
Current status and future prospects of biological routes to bio-based products using raw materials, wastes, and residues as renewable resources
Published in Critical Reviews in Environmental Science and Technology, 2022
Ji-Young Lee, Sung-Eun Lee, Dong-Woo Lee
Advanced biofuel production has been aided by metabolic engineering of microbial pathways in bacteria, yeast, and green algae (Liao et al., 2016; Zhang et al., 2011). The four major pathways targeted to date are (1) fermentative pathways, (2) 2-keto-acid pathways for short- and medium-chain alcohols, (3) isoprenoid pathways, and (4) fatty acid pathways (Figure 5). In the case of S. cerevisiae, expression of glycerol utilization genes, heterologous overexpression of key enzymes for fatty acid ester biosynthesis (wax ester synthase/acyl-coenzyme A:diacylglycerol acyltransferase), and deletion of genes involved in glycerol production enhanced the production of fatty acid ethyl esters (FAEEs) from glycerol, with a high FAEE yield and productivity (Yu et al., 2012). Moreover, heterologous expression of a 2-keto acid decarboxylase and an alcohol dehydrogenase (ADH) enabled E. coli cells to produce various short-chain alcohols (isobutanol, 3-methyl-1-butanol, 1-propanol, 1-butanol, and others) by diverting flux into amino acid bio-synthetic pathways (Atsumi et al., 2008). Similarly, an engineered Clostridium cellulolyticum strain could directly convert crystalline cellulose to isobutanol using its indigenous cellulases and amino acid biosynthesis pathway (Gaida et al., 2016; Higashide et al., 2011). Upon addition of ADH genes from E. coli and Lactococcus lactis, the pathway from 2-keto acid intermediates was diverted toward alcohol synthesis (Higashide et al., 2011). Using the same approach, a genetically-engineered Synechococcus elongatus strain could directly convert CO2 to isobutanol through photosynthesis, resulting in increased productivity due to overexpression of ribulose-1,5-bisphosphate carboxylase/oxygenase (Atsumi et al., 2009).