## 1 Introduction  
The industrial organism _Saccharomyces cerevisiae_ has traditionally been used in wine-making, baking, and brewing [1, 2]. This yeast has also been selected as a host for the development of first- and second-generation biofuel production, which utilizes either food biomass (corn starch, sugarcane) or lignocellulosic feedstocks (straw, corn stover, wood), respectively. _S. cerevisiae_ is also used to produce enzymes and pharmaceutical proteins such as hepatitis vaccine components, and it is being explored to make advanced biofuels, including farresene and isobutanol, as well as fine chemical compounds such as resveratrol or nootkatone [2]. The production of fuels and chemicals in biorefineries necessitates the use of robust strains that are resistant to industrial stresses, such as low pH, high ethanol concentrations, fluctuating temperatures, and the presence of different inhibitors [3]. To create strains for biorefinery applications, several genetic manipulations may thus be required to enable pathway alterations that will optimize the production of the desired product. Bioconversion of lignocellulosic biomass is gaining traction as a technique for generating biofuels and higher-value commodity products [4]. Biomass processing to produce bioethanol includes (i) chemical and/or physicochemical pre-treatment of biomass to make it susceptible to cellulolytic enzyme activity; (ii) enzymatic hydrolysis of pre-treated biomass components; and (iii) fermentation of the resulting hexose and pentose sugars [5]. The most basic conversion scheme is separate hydrolysis and fermentation (SHF), where each process is performed independently, allowing optimal conditions for the individual processes. However, it poses difficulties for industrial applications that include low conversion rates and the risk of contamination. By combining enzymatic hydrolysis with microbial fermentation of hexoses, simultaneous saccharification and fermentation (SSF) streamline and shorten the process stages [6]. However, both SHF and SSF require expensive exogenous enzymes, indicating that there is room for improvement in capital and operating costs. The most integrated bioconversion process is consolidated bioprocessing (CBP). All CBP processes, including enzyme synthesis, occur in a single reactor. CBP conversion of pre-treated lignocellulosic using a single microorganism or microbial consortium capable of producing the required enzymes and fermenting the resulting sugars into value-added products may provide economic benefits. However, CBP requires a microbial workhorse with the necessary phenotypes for enzyme synthesis, saccharification, and productivity [7; 8; 9; 10]. The major challenges in developing the industrial ethanologen _S. cerevisiae_ for effective microbial conversion of lignocellulosic biomass include heterologous expression of cellulolytic enzymes, engineering co-fermentation of hexose and pentose sugars, and ensuring resilience to different stressors [10]. Cellulose, hemicellulose, and lignin are the three major components of lignocellulosic biomass. Lignocellose is composed mostly of cellulose, which is a \(\beta\)-1,4 linked polymer of glucose, and glucose is the most abundant sugar in lignocellulosic hydrolysates [6]. The release of glucose monomers from cellulose requires the synergistic and coordinated activity of three main types of cellulases, namely: endoglucanases (EGs), exoglucanases such as cellobiohydrolases (CBHs), and \(\beta\)-glucosidase (BGLs) [9]. Heterologous expression of genes encoding cellulases from fungi or bacteria has been shown in recombinant strains of _S. cerevisiae_, including combined expression to create rudimentary cellulase systems [8; 10]. Strategies of heterologous cellulase expression, as well as examples of conversion of cellulosic substrates to ethanol by recombinant yeast strains, have been reviewed [11; 12].