# An Overview of the Alternative Use of Seaweeds to Produce Safe and Sustainable Bio-Packaging
## 4 Promising Seaweeds to Produce Bioplastics  
To define the quality of an optimal bioplastic, mechanical characteristics must be considered, such as tensile strength, elongation at break, thermal resistance, and water vapor permeability. Tensile strength is the maximum stress that a material can withstand while being stretched or pulled before breaking. Generally, the tensile strength and Young's modulus of plant fibers increases with increasing cellulose content of the fibers. Elongation at break is the ratio between changed length and initial length after breakage of the tested material. In a matrix with natural polymers, it expresses the ability to resist changes of shape without crack formation. Thermal resistance is a heat property, and represents the difference in temperature at which a material can resist [113]. Vapor permeability is a material's ability to allow a vapor (such as water vapor or, indeed, any gas) to pass through it. According to the ISO 11092:1993 [114], water vapor permeability is \"a characteristic of a textile material or composite depending on water vapor resistance\". The higher the value of the permeability of the material, the more rapidly water and vapor can pass through it. Films and bioplastics developed from seaweed-derived biopolymers that follow these characteristics are considered potential new materials to produce bio-packaging. Some current investigations on seaweeds employed in bioplastic production are summarized in Table 1. \begin{table}
\begin{tabular}{c c c c} \hline
**Seaweed** & **Extract/Compound in Biofilm** & **Biofilm Mechanical Characteristics** & **Reference** \\  & **Formulation** & & \\ \hline \multicolumn{4}{c}{Phylum Orthophyta, Class Phaeophyceae} \\ \hline \multirow{4}{*}{_Sargassum siliquosum_} & \multirow{2}{*}{Alginate} & Adequate tensile strength, elongation at break, water vapor permeability and water solubility due to addition of CaCl\({}_{2}\) & [59] \\  & & & \\  & & & of CaCl\({}_{2}\) \\ \hline \multirow{4}{*}{_Sargassum natans, Laminaria japonica_} & \multirow{4}{*}{Crude extracts} & Enhanced physicochemical, mechanical, and thermal properties due to addition of cellulose nanocrystals & [115] \\  & & & \\ \hline \multicolumn{4}{c}{Phylum Rhodophyta} \\ \hline \multirow{2}{*}{_Kappaphycus_ sp.} & \multirow{2}{*}{Crude extract} & Reduction in brittentess, weak tensile strength & [116] \\  & & & \\ \hline \multirow{2}{*}{_Kappaphycus alvarezii_} & \multirow{2}{*}{\(\kappa\)-carrageenan} & Evidenced good physical, mechanical and thermal strength of bioplastic films & [117] \\  & & & \\ \hline \multirow{2}{*}{_Eucheuma cottonii_} & \multirow{2}{*}{Semi-refined carrageenan} & Biofilm with refined carrageenan showed higher tensile strength and thermal resistance compared with semi-refined carrageenan & [118] \\ \hline \multirow{4}{*}{_Gracilaria salicornia_} & \multirow{4}{*}{Agar (photobleaching extraction)} & Tensile strength and elongation at break higher for biofilm obtained with agar from photobleaching extraction Thermal resistance and biodegradationhip in alkali extraction agar film & [119] \\  & & & \\ \hline \multirow{4}{*}{_Gracilaria vermiculophyllla_} & \multirow{4}{*}{Agar} & Transparency, clearness, flexibility, and mechanical strength enhanced by addition of glycerin & [77] \\  & & & \\ \hline \multirow{4}{*}{_Eucheuma spinosum_} & \multirow{4}{*}{Crude polysaccharides} & The addition of glycerol as plasticizer enhances biofilm physical and mechanical properties & [120] \\  & & & \\ \hline \end{tabular}
\end{table} 
Table 1: Seaweeds investigated for the development of biofilms for packaging manufacture. Seaweeds belonging to the genera _Kappaphycus_, _Eucheuma_, _Gracilaria_, _Porphyna_, _Gelitium_, _Pterocladia_ for red seaweeds, _Ullua_, _Codium_, _Enteromorpha_ for green seaweeds, and _Macrocytistis_, _Laminaria_, _Ascophyllum_, _Lessonia_ for brown seaweeds, have been investigated for their high polysaccharide content, which might allow the production of plastic biofilms [121].