The reactions of amino acids under subcritical water conditions in the temperature range 503-563 K using a pressure value corresponding to the saturated vapor pressure of water at the employed reaction temperature (hereafter called saturated subcritical water) were investigated. As reactants, solutions containing a single amino acid or a mixture of 17 different amino acids were used, and the obtained results in both cases were compared. Glysine, alanine, valine, and proline were produced as intermediate products during the thermal transformation of other amino acids. Generally, the results showed that the existence of amino acids together in a mixture decreased the overall stability since the activation energy values of decomposition of individual amino acids reduced significantly due to their presence in a mixture of amino acids. Most of the amino acids were found to be labile at acidic and near-natural pH values and more stable at a highly basic pH value.

The global accumulation of single‐use plastic bags made from nonbiodegradable plastics is the most concerning environmental issue nowadays. The utilization of biodegradable materials is a choice to reduce the environmental impact resulting from the use of plastic products. The utilization of renewable resources to produce fully biodegradable plastics is among the technologies used to overcome petroleum plastic's negative impact. On the other hand, the utilization of oxo‐biodegradable plastics where prodegradant additives are incorporated in conventional plastics to promote their degradation under certain conditions has recently received much attention. This review discusses the types and challenges that face the implementation of biodegradable plastics technology that uses renewable resources. This review also covers the debate addressed in the literature about the biodegradability fate of oxo‐biodegradable plastic in the air, compost, soil, landfill, and marine. A comparative study included the potential published literature in the last 10 years was performed. Based on the discussed evidence in this review, it can be concluded that all literature agrees that the addition of pro‐oxidant/prodegradants can accelerate the degradation of oxo‐plastics to small fragments. However, the complete biodegradation of oxo‐plastics by microorganisms remains in doubt. On the other hand, biopolymers produced from natural resources seem to be the future direction for plastics manufacturing especially single‐use plastic bags.

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This work presents the hydrolysis of a water-soluble protein, bovine serum albumin (BSA), for the production of both amino and organic acids under the sub-critical water condition in the temperature range of 200–300°C. The products of the reaction were a water-insoluble solid phase, an aqueous phase, and an insignificant gas phase which was neglected in this study. Results have shown that BSA passes through an aggregation step, followed by a gel formation process which results in the formation of insoluble solid aggregates. Then, such formed solids unfolded with releasing polypeptides as an intermediate product then finally hydrolyzed to produce low molecular mass products such as amino and organic acids. It was found that there were insignificant amino acids produced in the temperature ranges of 200–225°C within 2 min and 275–300°C within 0.5 min. However, by extending the reaction time, the protein transferred to both amino and organic acids.

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