# An Overview on Management and Valorisation of Winery Wastes
## 6 Wine By-Products as Raw Materials for Biopolymers and Natural Reinforcing Fillers  
Bio-based polymers may be directly extracted from biomass (Figure 3, Path 1), obtained by the polymerization of building blocks resulting from natural sources (Figure 3, Path 2), or synthesized by a direct microbial route (Figure 3, path 3) [107]. Bio-based polymers extracted from biomass, such as starch or cellulose (Path 1 from Figure 3), are mainly mixed with other polymer types, because their direct usage is difficult due to their intrinsic characteristics. The obtaining of bio-building blocks from renewable sources (Path 2 from Figure 3) is getting serious interest, resulting in sustainable polymers or other key bio-based chemicals. Furthermore, the microbial synthesis of polymers (Path 3 from Figure 3) gained importance due to the obtained polymers' versatile characteristics [107]. Figure 3: Bio-based polymers obtaining routes: (1) extraction from biomass; (2) polymerization of bio-based building blocks, and (3) microbial synthesis. Among biopolymers, one of the most important is polylactic acid (290 thousand tonnes in 2019) [108], which is a biodegradable linear aliphatic polyester synthesized by ring opening polymerization of lactone cyclic di-ester derived from lactic acid. Nowadays, lactic acid is industrially obtained from sugar or starch-rich biomasses, but research was conducted on using lignocellulosic sources to decrease the final polylactic acid price. In this respect, lignocellulosic vinc shoots are considered a promising substrate for lactic acid production (Table 6). Vine shoot hydrolysate (18 g/dm\({}^{3}\) xylose, 11 g/dm\({}^{3}\) glucose, and 4.3 g/dm\({}^{3}\) arabinose) was used as a carbon substrate for lactic acid synthesis by _Lactobacillus pentosus_, resulting in a final lactic acid concentration of 21.80 g/dm\({}^{3}\)[113]. Furthermore, the vine shoot hydrolysate used as the carbon substrate was combined with distilled white wine lees (20 g/dm\({}^{3}\)) as a source of nutrients, resulting in an encouraging volumetric productivity of 3.10 g/dm\({}^{3}\)h and a yield of 70% [112]. Several researchers used red and/or white lees as fermentative broth rich in nutrients [110; 111]. For example, 20 g/dm\({}^{3}\) wine lees resulted from the second decanting (as nutrient) and _Lactobacillus rhamnus_ (as microorganism) produced 105.50 g/dm\({}^{3}\) lactic acid with a volumetric productivity of 2.47 g/dm\({}^{3}\)h. Hemi-cellulosic hydrolysates from vine shoot trimmings were used as a carbon source for a two-stage bioreactor [115]. In the first stage, 31.50 g/dm\({}^{3}\) lactic acid was produced through glucose conversion by _Lactobacillus rhamnus_; in the second phase, xylose was fermented into xylitol by _Debaryomyces hansenii_[115]. Vine shoot hydrolysate was used to obtain, besides lactic acid, phenyllatic acid and biosurfactants by applying simultaneous saccharification and fermentation [114]. Polyhydroxyalkanoateates (PHAs) consist of biodegradable polyesters derived from 3-, 4-, 5-, and 6-hydroxyl-carboxylic acids. They often result from bacterial fermentation [116]. Depending on synthesis method, substrate, and process parameters, more than 150 types of hydroxyl-carboxylic acids can be obtained as PHA monomers [117], leading to  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Waste** & **Bacteria** & **Treatment** & **Fermentation** & **Lactic Acid (g/dm\({}^{3}\))** & **Yield (\%)** & **Productivity (g/dm\({}^{3}\) h)** & **Reference** \\ \hline \multirow{2}{*}{Grape pomace} & _Lactobacillus pentosus_ & Acid hydrolysis & Batch fermentation & 7.20 & 70 & 0.48 & [109] \\ \hline \multirow{4}{*}{Wine lees} & _Lactobacillus casei_ & Alkaline hydrolysis & Batch controlled with microwaves & \multirow{2}{*}{17.50} & \multirow{2}{*}{70} & \multirow{2}{*}{-} & [110] \\  & _Lactobacillus_ & & & & & & \\  
an extended spectrum of associated characteristics and uses of PHAs, for example, as thermoplastic polyolefins, elastomers, or adhesives [118].