Journal of Energy Bioscience 2024, Vol.15, No.6, 349-357 http://bioscipublisher.com/index.php/jeb 352 4.3 Improvements in fermentation efficiency using high-fiber feedstock High-fiber maize improves fermentation efficiency by providing a more stable and abundant supply of fermentable sugars. Genetically modifying maize to increase its cellulose and hemicellulose content has been the focus of recent research, aiming to accelerate the removal of lignocellulose in pre-fermentation treatments and improve processing convenience. Efficient fermentation processes, such as SSCF, have been optimized to effectively utilize fermentable sugars, resulting in higher ethanol titers and yields. For example, the SSCF process using Spathaspora passalidarum U1-58 achieved an ethanol titer of 53.24 g/L, demonstrating high fermentation efficiency when using high-fiber feedstocks. This highlights the potential of high-fiber maize to simplify the bioethanol production process, making it more efficient and higher yielding. 5 Case Study: Developing High-Fiber Maize for Bioethanol 5.1 Selection of target traits for high-fiber maize development Developing high-fiber maize for bioethanol production requires the identification and selection of specific traits that increase biomass yield and fiber content, thereby improving maize morphology. Key traits include high straw yield, increased fiber content, and good fiber composition. Studies have shown that the genetic diversity of maize germplasm can be used to improve these traits. For example, European landraces have a lower harvest index but higher fiber concentration, and have traits such as dense tolerance and lodging resistance, making them suitable candidates for breeding programs aimed at improving the quality of residues for bioethanol production (Munaiz et al., 2021). Identification of quantitative trait loci (QTLs) associated with grain quality and yield-related traits can also help in the selection of high-fiber maize varieties (Figure 1) (Sethi et al., 2023). Figure 1 Distribution of QTLs associated with quality and yield related traits (Adopted from Sethi et al., 2023) 5.2 Integration of breeding techniques in pilot programs In order to effectively integrate breeding technologies, it is imperative to combine traditional and modern methods. Multi-trait selection and genomic selection (GS) are particularly useful for the selection of varieties that require complex traits. By evaluating hybrids under different environments, multi-trait selection can improve multiple desirable traits simultaneously, such as grain yield and fiber content (Ruswandi et al., 2023). On the other hand, whole genome selection uses genotype data to predict and select individuals with target traits, thereby accelerating the breeding process. This approach has been successfully applied to tropical maize breeding programs. Tropical maize has the advantages of rich genetic diversity, strong resistance, and good green retention. Its excellent genes can be used to improve grain yield and other agronomic traits (Beyene et al., 2021). High-throughput phenotyping methods, such as near-infrared spectroscopy (NIRS), can also be used to more effectively evaluate complex traits such as crop growth and yield, and provide timely feedback on various stress conditions encountered by crops (Cabrera-Bosquet et al., 2012).
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