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Metabolic Engineering for the Production of a Variety of Biofuels and Biochemicals
Published in Kazuyuki Shimizu, Metabolic Regulation and Metabolic Engineering for Biofuel and Biochemical Production, 2017
Under oxygen limitation, a mixed acid fermentation occurs, producing a wide spectrum of metabolites such as acetate, lactate, formate, succinate, ethanol, acetoin, and 2,3-BDO, originating mostly from pyruvate (except succinate that is from PEP), the end product of the glycolysis (Fig. 17). For 2,3-BDO synthesis from pyruvate, three enzymatic reaction steps are involved, where two moles of pyruvate is condensed with a single decarboxylation to form a-acetolactate by a-acetolactate synthase (ALS, EC 4.1.3.18), where ALS is active under slightly acidic and anaerobic conditions, and inactive under aerobic conditions. The genes encoding ALDC, ALS, and BDH are clustered in one operon as budABC in K. ferrigena and E. aerogenes (Blomqvist et al. 1993), where this operon seems to be under control of the putative fumarate nitrate reductase (FNR), which is active under anaerobic conditions (Mayer et al. 1995). The a-acetolactate is then converted to acetoin by a-acetolactate decarboxylase (ALDC, EC 1.1.1.5), and acetoin is converted to 2,3-BDO by NADH dependent 2,3-BD dehydrogenase (BDH, EC 1.1.1.76) (also called as acetoin reductase, EC 1.1.1.4) (Ji et al. 2011), where different isomeric forms of 2,3-BDO is formed by the action of different BDH with different stereospecificities, or by a cyclic pathway (known as butandiol cycle) (Sabra et al. 2016).
Herbicide-Resistant Weeds
Published in Yeqiao Wang, Landscape and Land Capacity, 2020
Cross-resistance is the expression of one mechanism that provides plants with the ability to withstand herbicides from different chemical classes.[2] For example, a single point mutation in the enzyme acetolactate synthase (ALS) may provide resistance to five different chemical classes including the widely used sulfonylurea and imidazolinone herbicides.[3] However, cross-resistance at the whole-plant level is difficult to predict because a different point mutation in the ALS enzyme may provide resistance to one chemical class and not others. Cross-resistance also can result from increased metabolic activity that leads to detoxification of herbicides from different chemical classes.
Pesticides
Published in José L. Tadeo, Analysis of Pesticides in Food and Environmental Samples, 2019
José L. Tadeo, Beatriz Albero, Rosa Ana Pérez
One type of herbicides causes the inhibition of acetolactate synthase (ALS), the first common enzyme in the branched-chain amino acid biosynthetic pathway. ALS inhibitors include, among others, herbicides of the sulfonylurea family. These compounds vary greatly in selectivity, some of them being extremely active.
Remedial capacity of diclosulam by cover plants in different edaphoclimatic conditions
Published in International Journal of Phytoremediation, 2021
Cícero Teixeira da Silva, Gabriela Madureira Barroso, Daniel Valadão Silva, Leandro Galon, Cinthia Maethê Holz, Márcia Vitória Santos, Anderson Barbosa Evaristo, Paulo Sérgio Fernandes das Chagas, Alisson José Eufrásio de Carvalho, José Barbosa dos Santos
Diclosulam is a herbicide belonging to the group of triazolopyrimidines, most commonly used in soybean and sugarcane crops (Oliveira Júnior 2011; MAPA – BRASIL 2020), despite being a molecule without European Union regulatory approval for use (Lewis et al., 2016). This herbicide inhibits the enzyme acetolactate synthase (ALS), which is essential for the synthesis of the amino acids valine, leucine, and isoleucine (Xu et al. 2015). Its solubility in water depends on the pH; it varies from 100 mg kg−1 (pH 5–7) to 4,000 mg kg−1 (pH 9). The pKa of the molecule ranges from 4.09 to 20, acidic with a predominance in anionic form at pH values characteristic of agricultural soils (Lavorenti et al. 2003). Its logKow values range from −0.448 (at pH 9) to 1.42 (at pH 5), indicating low hydrophobicity (Yoder et al. 2000). Diclosulam has a long residual effect that varies depending on the soil moisture and clay and organic matter contents (Lavorenti et al. 2003). The main factors that influence its sorption in the soil are the edaphoclimatic conditions and levels of organic matter in the soil (Bonfleur et al. 2016).
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
Other essential biofuels from microbial conversion include 1,3-propanediol (1,3-PDO), 2,3-BDO, and butanol (Table 2 and Figure 4). Citrobacter freundii FMCC-B 294, under fed-batch fermentation conditions, produced 1,3-PDO using raw glycerol as substrate (Metsoviti et al., 2013). Similar results were observed using Klebsiella pneumoniae DSM 4799 under fed-batch conditions with raw glycerol as substrate (Jun et al., 2010). Furthermore, large-scale approaches can be successfully performed using Clostridium butyricum AKR102a, since 1,3-PDO was produced in a 200 L fermentation vessel (Wilkens et al., 2012). Additionally, raw glycerol-derived biodiesel is assimilated by C. butyricum NRLL B-23495 to produce 1,3-PDO through batch fermentation under anaerobic conditions, while Enterobacter aerogenes produces 2,3-BDO in shake-flasks, and C. freundii produces ethanol (Metsoviti et al., 2012). Strains of Klebsiella, Enterobacter, Serratia and Bacillus are major producers of 2,3-BDO (Song et al., 2019). Three enzymes, acetolactate synthase (Als), acetolactate decarboxylase (AldC), and butanediol dehydrogenase (Bdh), are necessary to convert pyruvate to α-acetolactate, acetoin, and 2,3-butanediol, respectively (Yang et al., 2016). For instance, Enterobacter cloacae produces 93.9 g/L of 2,3-BDO from cassava powder in fed-batch SSF (Wang et al., 2012). To improve the efficiency of 2,3-BDO production, genes involved in byproduct-producing paths were knocked out. For instance, deletion of lactate dehydrogenase diverted carbon flux from lactate production to 2,3-BDO biosynthesis in E. aerogenes (Jung et al., 2012).