Journal of Energy Bioscience 2024, Vol.15, No.4, 267-276 http://bioscipublisher.com/index.php/jeb 273 to enhance bioethanol yields (Sulfahri et al., 2020). Additionally, the cultivation and fermentation of marine microalgae like Navicula sp. strain TAD highlight the feasibility of using microalgae as a sustainable feedstock for bioethanol production (Telussa et al., 2023). These lessons emphasize the need for continued research into optimizing fermentation processes, improving microorganism strains, and developing cost-effective pretreatment methods to advance the field of marine-based bioethanol production. 7 Challenges and Future Perspectives 7.1 Technical challenges The utilization of marine microorganisms for large-scale bioethanol production presents several technical challenges. One significant limitation is the need for effective pretreatment methods to break down the complex cell walls of marine biomass, which is crucial for efficient saccharification and fermentation processes (Soliman et al., 2018; Sulfahri et al., 2020). Additionally, the presence of various inhibitors in seaweed hydrolysates, such as salts, can negatively impact the fermentation efficiency of marine yeasts (Turner et al., 2022). Another challenge is the metabolic engineering required to enable microorganisms to degrade and assimilate specific polysaccharides found in marine biomass, such as alginate from brown algae (Takeda et al., 2011). The development of robust microbial strains that can tolerate high concentrations of glucose, xylose, and ethanol is also essential for improving bioethanol yields (Turner et al., 2022). 7.2 Environmental and economic considerations Marine-based bioethanol production has the potential to be more environmentally sustainable compared to traditional bioethanol production methods. Utilizing marine biomass, such as algae, does not compete with food crops for land and freshwater resources, thereby reducing the environmental footprint (Greetham et al., 2018; Ramachandra and Hebbale, 2020). However, the economic viability of this approach is still a concern. The high costs associated with pretreatment and nutrient supplementation during fermentation need to be addressed to make marine bioethanol production commercially feasible (Sulfahri et al., 2020). Additionally, the large-scale harvesting of marine biomass must be managed sustainably to avoid negative impacts on marine ecosystems (Soliman et al., 2018; Reisky et al., 2019). 7.3 Future research directions Future research should focus on developing more efficient and cost-effective pretreatment methods to enhance the breakdown of marine biomass. Exploring alternative nutrient supplementation strategies, such as the use of fungal biomass, could also improve the economic viability of marine bioethanol production (Sulfahri et al., 2020). Further studies are needed to understand the metabolic pathways of marine microorganisms better and to engineer strains with enhanced capabilities for bioethanol production (Takeda et al., 2011; Adegboye et al., 2021). Additionally, research should investigate the potential of using seawater as a fermentation medium to reduce freshwater consumption and improve the sustainability of the process (Greetham et al., 2018; Zaky et al., 2020). Finally, comprehensive life cycle assessments and economic analyses are essential to evaluate the overall feasibility and environmental impact of marine-based bioethanol production (Ramachandra and Hebbale, 2020). 8 Concluding Remarks This research has explored the potential of marine microorganisms in the fermentation process for bioethanol production. Key findings include the successful use of both macroalgae and microalgae as feedstocks, with marine yeasts demonstrating high tolerance to salt and inhibitors, making them suitable for seawater fermentation. Metabolically engineered bacteria, such as Sphingomonas sp. A1, have shown promise in converting alginate from brown algae into ethanol, achieving significant ethanol yields. Additionally, the marine yeast Wickerhamomyces anomalus M15 has been characterized for its high tolerance to various inhibitors and its potential for industrial bioethanol production using seaweed-derived feedstocks. The enzymatic hydrolysis and fermentation of microalgae like Chlorella vulgaris have also been highlighted as effective methods for bioethanol production. The utilization of marine microorganisms and biomass presents a sustainable and environmentally friendly alternative to traditional bioethanol production methods. Marine yeasts and bacteria can thrive in saline conditions,
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