## 1 Introduction  
Contemporary society exhibits heightened interest in the advancement of technologies for sustainable energy generation utilizing renewable resources [1]. AD, specifically the biotransformation of organic waste into biogas, presents a viable pathway within this domain. This process yields multifaceted benefits [2]. Environmentally, biodegradation facilitates a reduction in both the volumetric and organic load of waste materials, thereby mitigating potential ecological perturbations associated with improper waste disposal. Economically, the generation of biogas, a high-calorific renewable fuel, is coupled with a concomitant decrease in expenditures related to waste management and disposal [3]. Amidst escalating climate change concerns, biogas production as a renewable energy source has garnered substantial research attention over the recent decades. Optimizing sustainable hydrogen and methane yields from waste substrates creates some technological hurdles. A two-stage AD strategy, incorporating enhanced hydrolysis to augment the subsequent methanogenesis, has been proposed to maximize the energy recovery from biodegradable organic waste [4]. Hydrogen (H\({}_{2}\)), envisioned as a future fuel, offers a high energy density and calorific value, with the added advantage of carbon-neutral combustion [5]. Dark fermentation enables H\({}_{2}\) production from renewable feedstocks. Methane (CH\({}_{4}\)), a versatile energy carrier, can be utilized for heat and power generation, as well as being a gaseous vehicular fuel, thereby offering a substitute for natural gas [6]. The AD of diverse organic substrates, encompassing both monosubstrates and heterogeneous blends, has been investigated for biogas generation [7]. The substrate composition significantly modulates the efficiency of the individual digestion stages. Corn steep liquor (CSL), a byproduct of corn wet milling, serves as a versatile industrial feedstock and microbial growth supplement in fermentative processes yielding biofuels, enzymes, and organic acids [8]. The substantial generation of CSL, a readily available waste stream from corn starch production, poses significant environmental challenges [9]. Consequently, research efforts are directed towards its valorization in biotechnological applications, including fructo-oligosaccharide, natamycin, lipid, and docosahexaenoic acid biosynthesis, as well as its utilization as an additive in fresh rice straw silage fermentation [10]. Improved cordycepin production in _Cordyceps militaris_ was achieved through various strategies by specific strain and culture conditions, and utilizing alternative nitrogen sources such as CSL [11]. Corn steep liquor was proven to also be a key ingredient in the manufacture of penicillin [12]. As a sustainable energy source with a high energy yield, hydrogen is a promising alternative to fossil fuels. Co-digestion involves the simultaneous fermentation of multiple substrates and offers opportunities to improve biohydrogen production through synergistic interactions between different waste materials [13]. Hydrogen and methane play a role as energy vectors because both can store, transport, and deliver energy and serve as a medium that allows for the storage and transport of energy from renewable sources, with the aim of further use in various applications like power, transport, or heat [14]. The two-stage AD concept consisting of a hydrogenic process followed by a separate methanogenic process has been suggested as a tool to completely utilize the organic acids produced during dark fermentation and to improve the overall energy conversion efficiency [15]. Most anaerobic reactors do not provide ideal conditions for both acidogenic and methanogenic microorganisms. When the stages are separated, the different microbes receive their favorable environment. The application of two-step processes allows the acidification and methanogenesis phases to be physically separated [4].