# An Overview on Management and Valorisation of Winery Wastes
## 8 Conclusions and Future Perspectives  
This literature review highlighted a lack of sustainable and integrated usage of winery wastes. This study has reviewed the potential use of winery wastes, such vine shoots, grape pomace, and wine lees, as raw materials for various applications, in order to keep resources in use as long as possible, extracting their maximum value whilst in use, and recovering and regenerating products and materials at the end of their service life. Due to their antimicrobial and antibacterial activity, and synergism with antibiotics, winery wastes may be used to manage antibiotic resistance while solving another worldwide problem, the environmental sustainability of agricultural activity. The high content of bioactive compounds, such as polyphenols, makes these wastes a promising source for new antibacterial agents. Agricultural residues such as winery wastes have been pointed out as potential adsorbents for wastewater treatment. Transitional metal ions from wastewater are bound though functional groups such as hydroxyl, amino, or carboxyl, in proteins or phenolic compounds. Wine by-products have been applied as carbon source for the microbial production of important polymer precursors, such as lactic or succinic acid. Likewise, grape stalks were used a raw material for the microbial synthesis of polymer precursors. However, even if they have a higher conversion yield, they have been used as carbon sources less frequently than vine shoots, due to their high content of antimicrobial tannins bonded with structural lignin, which are difficult to remove. In this respect, further investigation must be done to improve the detoxification treatment for tannin removal. The optimal valorisation path of grape pomace is the recovery of tartaric acid which can be further transformed into succinic acid to produce biopolymers. Wine lees, predominantly containing salts and dead yeast, have been used as nutrient medium, offering a low-cost option compared with commercial yeast extracts. Furthermore, wine wastes have been applied as reinforcing filler biopolymers such as polylactic acid, polybutylene succinate, or poly-3-hydroxybutyrate-co-3-hydroxyalerate. In terms of mechanical characteristics, wine wastes can enhance the biopolymer stiffness and lower their tensile strength. Since each study tested wine wastes without any preliminary treatment, it is rational to imagine that wine filler surface treatment, such as acetylation or silanization, will enhance this characteristic. Further research must be done to test residual wine solids resulting from the biopolymers synthesis, and assessing the possibility of obtaining wine-derived plastics in line with a circular economy. Even though various studies were achieved using grape pomace for different applications that could be applied by small- or medium-scale industrial producers, an integrated process including chemical, biochemical, and thermal treatments may be essential to maximally valorise this agricultural waste to produce a low-cost raw material. Grape pomace usage as a pectin source represents a promising future perspective. Consequently, its recovery from grape pomace, along with bioactive components and even oil, constitutes an attractive outlook for waste valorisation in terms of economic and environmental sustainability. Furthermore, grape pomace valorisation gained an increased interest from the food industry, with pectin extraction being the compelling argument for further intense investigation. Moreover, the most important components from grape pomace, dietary fibre and polyphenols, were identified as fortification elements for food. It was observed that the addition of grape pomace increased the total polyphenic content, but, sometimes, the fortification also led to modification of sensory properties. In this respect, individual food commodities must be further tested separately for potential grape pomace fortification.