Journal of Energy Bioscience 2024, Vol.15, No.4, 267-276 http://bioscipublisher.com/index.php/jeb 270 processes (Greetham et al., 2018; Turner et al., 2022). Nutrient availability, including the presence of essential minerals and vitamins, can significantly impact microbial growth and ethanol yield. Additionally, the presence of inhibitors, such as salts and other by-products, can affect fermentation efficiency, necessitating the use of tolerant strains or adaptive evolution techniques to enhance performance (Turner et al., 2022). 4 Metabolic Pathway Analysis 4.1 Glycolysis in marine microorganisms Glycolysis is a fundamental metabolic pathway that converts glucose into pyruvate, generating ATP and NADH in the process. In marine microorganisms, glycolysis operates similarly to terrestrial organisms but with adaptations to their unique environments. For instance, the cyanobacteriumSynechococcus sp. PCC 7002 has been shown to maintain high glycolytic activity even under the stress of ethanol production, which is crucial for bioethanol synthesis (Kopka et al., 2017). Additionally, the overexpression of transcription factors such as ZNF1 in Saccharomyces cerevisiae has been demonstrated to enhance glycolytic flux, thereby improving bioethanol productivity under high glucose concentrations (Songdech et al., 2020). These findings suggest that marine microorganisms can be engineered to optimize glycolysis for efficient bioethanol production. 4.2 Pyruvate decarboxylation and ethanol production The conversion of pyruvate to ethanol involves two key enzymes: pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH). In marine microorganisms, this pathway is often engineered to enhance ethanol yield. For example, the introduction of PDC and ADH from Zymomonas mobilis into Synechocystis sp. PCC 6803 has enabled the photoautotrophic conversion of CO2 to ethanol (Dexter and Fu, 2009). Similarly, overexpression of these enzymes in Escherichia coli has resulted in high ethanol production, although it also led to significant metabolic rewiring (Yang et al., 2014). These modifications highlight the potential of marine microorganisms to be tailored for efficient ethanol production through targeted metabolic engineering. 4.3 Alternative pathways Marine microorganisms may also utilize alternative metabolic pathways for bioethanol production. For instance, the thermophilic bacteriumGeobacillus thermoglucosidasius employs a mixed acid fermentation process under anaerobic conditions, producing ethanol along with lactate, acetate, and formate (Tang et al., 2009). This bacterium's ability to ferment both C5 and C6 sugars and tolerate high ethanol concentrations makes it a promising candidate for bioethanol production. Additionally, the rerouting of glycolytic carbon to alternative products such as lactate and glycerol has been observed in Chlamydomonas reinhardtii mutants lacking pyruvate formate lyase and alcohol dehydrogenase, indicating the flexibility of metabolic pathways in response to genetic modifications (Catalanotti et al., 2012). These alternative pathways provide insights into the diverse metabolic capabilities of marine microorganisms and their potential applications in bioethanol production. By understanding and manipulating these metabolic pathways, researchers can enhance the efficiency and yield of bioethanol production in marine microorganisms, contributing to the development of sustainable biofuels. 5 Technological Integration and Optimization 5.1 Bioreactor design for marine microorganisms Designing bioreactors that can support marine microorganisms involves addressing several unique challenges. Marine microorganisms often require specific environmental conditions, such as high salinity and particular temperature ranges, which must be maintained consistently within the bioreactor. The use of seawater as a medium, as highlighted in recent studies, can be beneficial due to the natural tolerance of marine microorganisms to salt and inhibitors, making them suitable for seawater fermentation (Greetham et al., 2018). Additionally, the integration of advanced control systems, such as optogenetic tools, can enhance the precision of metabolic control within the bioreactor. For instance, light-controlled transcription can be used to shift cells between growth and production phases, optimizing the fermentation process (Zhao et al., 2018). Furthermore, the co-culture of different engineered organisms within the same bioreactor can be employed to distribute metabolic pathways, thereby enhancing the production of complex metabolites (Zhou et al., 2015).
RkJQdWJsaXNoZXIy MjQ4ODYzMg==