## 1 Introduction  
Presently, the global community, with an aim to shape the future of bioeconomy, has put together rigorous efforts on the biorefining of biomass feedstocks [1]. These substrates, specifically the lignocellulosices due to their relative abundance and readily collectable nature, have become quite prominent candidates in this race [2]. However, their inclusive utilization still demands new technological processes to expand their boundaries for the production of sustainable products within the context of a biorefinery [3]. Among various lignocellulosices, pine wood biomass, a softwood, is an important feedstock with second highest contents (up to 30% on average) as lignin within their native biomass matrix [4]. This lignin, being an important macromolecule, is primarily composed of varying units of guiaacyl (G units in pine wood biomass), syringl (S units), and p-hydroxyphenyll (H units) depending on the type of biomass species [5; 6]. Lignin, with the presence of phenolic groups in its molecule, has become quite a versatile feedstock for the production of various sustainable materials [7]. These can be used for the production of rubbers, poly propylene, epoxy resins, and even carbon fibers [8; 9; 10]. Even more, this lignin can also be used as a partial substitute for the petroleum based resins minimizing thus the harmful impacts of toxic substances. However, the lignin structure strongly varies with the adapted isolation process [11]. For example, lignin isolated via widely employed processes (such as Kraft, sulfite, organo-solv, soda, etc.) differ widely not only among their molecular weights but also in their functional groups [11]. Although pulp and paper industry widely use the pulping processes (Kraft and sulfite) for lignin isolation, such kind of lignin offers less reactivity with high impurities and even so with severely modified structures making them less likely to be used for wider industrial applications [12; 13]. Literally, there have been some good strategies to isolate the proto lignin including the famous milled wood lignin (MWL) and enzymatic lignin processes [14; 15]. Similarly, the organosolv processes, taking advantage of organic acids, alcohols, or even from their synergistic effects, have also been found effective to extract the prototype lignin ensuring the solvent recovery as an additional benefit [16]. Recently gamma valerolactone (GVL) has been investigated as a potential reagent for the dissolution and extraction of lignin from lignocellulosicoses [17; 18]. This organic solvent is a self-sustained product within a lignocellulosic biorefinery and is capable enough to extract lignin at near neutral solvent conditions [19]. Typically, GVL/acid/water has been mostly applied for an enhanced delignification rate with an improved cellulose digestion [20]. Being miscible with water, it induces better hydrolytic effects for biomass to dissolve out lignin [21]. It has also been applied under synergetic effects with metal salts, microwave, and with acids [22; 23]. Additionally, there is a fair deal of studies on the lignin isolation from biomass species using both the dioxane and acetic acid as it has been reported that the acidic conditions effectively break the most frequent arylalkyl ether bonds and lignin carbohydrate complex leading to the formation of low molecular weight lignin. However, increasing thermal and acidic severity can cause lignin condensation [24]. Acetsolv is another one such process in which xylan portion of the biomass is dissolved by breaking glycosidic bonds with the help of acetic acid and also this acid catalyzes the cleavage of \(\beta\)-O-4 linkages to yield soluble low weight aromatics. However, more severe conditions of hydrogen ions not only increase the hydrolysis but also degrade the secondary sugars [25].