Journal of Energy Bioscience 2024, Vol.15, No.4, 267-276 http://bioscipublisher.com/index.php/jeb 271 5.2 Genetic engineering approaches Genetic engineering plays a crucial role in enhancing ethanol yield and efficiency in marine microorganisms. By modifying metabolic pathways, it is possible to increase the tolerance of microorganisms to high ethanol concentrations and improve their overall productivity. Techniques such as metabolic engineering and synthetic biology have been extensively used to redirect carbon fluxes towards the desired products. For example, engineering microbes to balance cellular redox metabolism can optimize microbial production by overcoming cellular redox limitations (Kracke et al., 2018). Additionally, the development of microbial cell factories through systems metabolic engineering can lead to the construction of industrial strains with optimized pathways for ethanol production, increased tolerance to inhibitors, and enhanced genetic stability (Gustavsson and Lee, 2016). The use of computational tools like Flux Balance Analysis (FBA) can further aid in designing efficient metabolic networks by predicting biomass growth and metabolic flux distribution under various environmental conditions (Sen, 2022). 5.3 Process optimization Optimizing the fermentation process for higher yield and lower costs involves several strategies. One effective approach is the integration of artificial neural networks with genetic algorithms (ANN-GA) to model and predict optimal fermentation conditions. This method has been successfully applied to marine macroalgal biomass, resulting in significant improvements in bioethanol yield (Dave et al., 2021). Additionally, the use of high-throughput, small-scale fermentation techniques can accelerate the screening and characterization of engineered strains, thereby identifying the most promising candidates for large-scale production (Raj et al., 2021) (Figure 1). The combination of metabolic flux analysis tools with bioreactor control algorithms can also help in fine-tuning the fermentation process, ensuring optimal conditions for microbial growth and product formation (Hollinshead et al., 2014). By employing these advanced techniques, it is possible to achieve a more efficient and cost-effective bioethanol production process using marine microorganisms. 6 Case Studies 6.1 Successful implementation examples Several case studies have demonstrated the successful use of marine microorganisms in bioethanol production. For instance, the marine yeast Wickerhamomyces anomalus M15 has shown significant potential in fermenting seaweed-derived media, producing up to 92.7 g/L ethanol from 200 g/L glucose (Turner et al., 2022). Another example is the marine yeast Saccharomyces cerevisiae AZ65, which achieved an ethanol concentration of 113.52 g/L using seawater-based media (Zaky et al., 2020). Additionally, the marine flavobacteriumFormosa agariphila has been utilized to degrade ulvan from Ulva species into fermentable monosaccharides, showcasing the potential of marine bacteria in bioethanol production (Reisky et al., 2019). Furthermore, the use of fungal pretreatment of marine macroalgae has been shown to increase ethanol yields by up to 38.23% (Sulfahri et al., 2020). Lastly, the marine microalgae Navicula sp. strain TAD has been successfully cultivated and fermented to produce bioethanol, indicating the viability of microalgae as a feedstock (Telussa et al., 2023) (Figure 2). 6.2 Comparative analysis Comparing these case studies reveals different approaches, microorganisms, and outcomes. Wickerhamomyces anomalus M15 and Saccharomyces cerevisiae AZ65 both demonstrated high ethanol production, but the former showed better performance in concentrated seaweed hydrolysates (Zaky et al., 2020; Turner et al., 2022). The enzymatic degradation pathway of Formosa agariphila highlights a bacterial approach, focusing on breaking down complex polysaccharides into fermentable sugars (Reisky et al., 2019). In contrast, the fungal pretreatment method emphasizes the use of fungi to enhance saccharification and nutrient supplementation, leading to higher ethanol yields (Sulfahri et al., 2020). The use of Navicula sp. strain TAD represents a microalgal approach, focusing on the cultivation and hydrolysis of microalgae for bioethanol production (Telussa et al., 2023). Each method has its unique advantages and challenges, such as the need for specific pretreatment processes or the tolerance of microorganisms to high salt concentrations.
RkJQdWJsaXNoZXIy MjQ4ODYzMg==