<div class="text-justify">Greetings my friends. We are all aware of the great problems that have generated the use of synthetic plastics, those derived from raw materials of petrochemical origin, such as polyethylene, polypropylene, PET or PVC to name a few. Mainly because these materials are not biodegradable, so their accumulation in the environment represents a great problem of pollution, besides that, they can release harmful substances to health. So it is urgent to find a more ecological alternative for these materials.

<center>![biop1.jpg](https://images.hive.blog/DQmVQCPMpYATrWh75rUry4ccynwXWzUczx2tdtBbRGPr9aC/biop1.jpg)
**_Image designed by @emiliomoron, contains in the background a [public domain image.](https://pixabay.com/es/photos/musgo-vegetaci%C3%B3n-bokeh-de-fondo-983908/)._**</center>

We know that it is difficult to imagine a world without plastics, thanks to the strength and great capacity they have to be molded into different shapes, they have become very desirable materials for all kinds of applications. These materials, in addition to having found a place of excellence in the packaging industry and product packaging, are used in the construction industry, transportation, furniture, household items and electronics and sports. And due to such favorable characteristics as: high resistance and low weight, excellent barrier to protect products from air and water, and added to a low cost, they are very difficult to replace.

So, since it is difficult to do without them due to the current needs of our society, perhaps we should pay more attention to bioplastics as an alternative to reduce pollution from the accumulation of plastic waste of synthetic origin, since these are polymers that are derived from natural and renewable sources, and have a much higher rate of biodegradation than conventional plastics.

## Let's clarify what a bioplastic is
The term bioplastic is used to refer to different types of materials made from biopolymers of plant origin, those using raw materials of agricultural origin being the most studied.  Especially starch and cellulose are the main source for obtaining bioplastics, which are natural polymers made by plants, and are obtained mostly from vegetable waste such as potato, corn, yucca and wheat among others. 

The name biopolymer covers two types of molecules, on the one hand those synthesized by living organisms, such as cellulose, and on the other hand those resulting from the polymerization of basic molecules from renewable sources, such as lactic acid. The alteration of the structure of a biopolymer by means of a dispersing agent transforms it into a bioplastic[1].

<center>![Imagen3.jpg](https://images.hive.blog/DQmWhTFqFqjvLdP2EET4tNU9DQdC1rCfDt1SqHybAdnYtnL/Imagen3.jpg)
**_Cellulose structure. A biopolymer composed of glucose molecules. Source: [Wikimedia Commons, CC0](https://commons.wikimedia.org/wiki/File:Cellulose_strand.svg)._**</center>

Biopolymers are macromolecules present in living organisms, such as proteins, polysaccharides, polyphenols such as lignin or polyterpenes, the latter including natural rubber.

The idea is to use chemical structures that allow the material to be naturally degraded by microorganisms, something that cannot occur with petroleum derivatives such as polyethylene or polystyrene. 

<center>![biop2.jpg](https://images.hive.blog/DQmdQM9bqRRAQSAnk5Mf89VL21nZtHPghd2WmC6pkvgQ4yT/biop2.jpg)
**_The goal is for the bioplastic to be naturally deaggregated. Image designed by @emiliomoron, contains in the background a [public domain image.](https://pixabay.com/es/photos/abono-compostaje-el-compostaje-5009027/)_**</center>

## A little bit of the state of the art
Cellophane was the first bioplastic developed, made from vegetable cellulose in 1912, but due to the production of cheaper synthetic plastics better adapted to mass production it was displaced [2]. 

It would take a few decades for polyamide 11, a bioplastic derived from castor oil, to enter the market in 1947. It would become the first bioplastic introduced into the market due to its excellent chemical and mechanical properties, since it could be heated and molded in different ways [3]. However, bioplastics were still a niche product due to their high cost.

In the 90's the most well known plastics appeared at present, PLA (polylactic acids), PHAs (polyhydroxyalkanoates), the first ones were obtained from polymerized lactic acid through the fermentation of lactic bacteria with corn starch, while PHAs are a type of polyesters produced by the fermentation of bacteria with organic substrates such as glucose, sucrose, alcohols, organic acids and hydrocarbons. This boom in bioplastics came about thanks to rapid advances in green chemistry and the revival of interest in bioplastics, as the environmental costs associated with the production of millions of tons of non-biodegradable plastics became apparent by the end of the 20th century. 

By 2011, the production of bioplastics increased, doubling by 2015, as they were incorporated into a greater number of applications, from packaging to toy manufacturing. 

In addition to other new polymers that are emerging, the main changes are based on the diversification of the raw material, focused mainly on the use of waste from different biomass, such as corn, potatoes and wheat among others.

<center>![biop3.jpg](https://images.hive.blog/DQmSriq9CpBuitfHjLGeFbTzBnCAc95hxsdsCsUSqJSwb8k/biop3.jpg)
**_Brief chronology of the evolution of bioplastics. Source: @emiliomoron, image elaborated in Powerpoint with information of the consulted sources._**</center>

## Biodegradability of bioplastics
Biodegradability is defined as the type of decomposition through which some products and substances are disintegrated by the action of certain biological organisms, such as bacteria, insects, fungi, algae, etc.[4], transforming organic contaminants into less dangerous compounds that can be integrated into natural biochemical cycles. 

Bioplastics can be degraded by the action of microorganisms, by chemical decomposition, photodegradation or a combination of these. The degradation of bioplastics begins by breaking the polymer chains through a hydrolysis reaction, followed by the destruction of the bonds by the effect of light and the action of aerobic bacteria. Or when they are buried, for example in landfills, it proceeds by the enzymatic action of anaerobic bacteria[4].

<center>![biop4.jpg](https://images.hive.blog/DQmUrwr7ggPaLusJUHwrfFjfvsRaap7UG8VPf9HGefssf5J/biop4.jpg)
**_Life cycle of a bioplastic product. Source: image elaborated by @emiliomoron._**</center>

## Difference between bioplastic and biodegradable plastic
It should be noted that there are biodegradable plastics that are derived from petroleum, so they should not be confused with bioplastics. The term biodegradable plastic may include petroleum-based plastics that contain additives to enhance their ability to degrade in the environment but do not meet some international standards for biodegradation, such as ISO-14855. While bioplastics are only derived from natural, renewable sources, so they do meet these standards.

Generally, bioplastics tend to degrade in periods less than a year, generating as waste carbon dioxide, biomass and water. In contrast to conventional plastics that can persist in the environment for a long time.

<center>![biop5.jpg](https://images.hive.blog/DQmTCXSEa8T3LKjLR5kN2vfBhj2kVvhbD9cz15E7rCNtGHu/biop5.jpg)
**_Bolsa plástica a base de celulosa, etiquetada como biodegradable. Fuente: [Wikimedia Commons, CC BY-SA 4.0](https://commons.wikimedia.org/wiki/File:Sonali_Bag.jpg)_**</center>

## Starch as a raw material for bioplastics
Starch, a natural polymer that can be obtained from corn or potatoes, is widely used in the manufacture of bioplastics. Starches are composed of macromolecules organized in layers, which are formed by two different polymeric structures, amylose and amylopectin. Amylose molecules are located in the lower layers and can be composed of 200 to 20000 glucose molecules linked by glycosidic bonds in unbranched chains[5].

Milopectin is located in the outer layers, the molecules are linked by glycosidic bonds α-1,4 and α-1,6 and have branches in the main chain, which are due to this type of linkage. These molecules are significantly larger than amylose molecules, and can have up to 20 million glucose units.

<center>![Imagen5.jpg](https://images.hive.blog/DQmW3XSYMPRCfe5v8c6V229EPd89B5RCYRoHxJhcnZHZyUL/Imagen5.jpg)
**_Starch is made up of two compounds: a) amylose and b) amylopectin. Source: [Wikipedia.com.](https://es.wikipedia.org/wiki/Almid%C3%B3n)_**</center>

To convert starch into raw material for bioplastics, it is necessary to break and melt its structure. In addition, it is essential to add plasticizing additives, without which it would not have the appropriate properties to work as a thermoplastic; these additives improve the flexibility of starch and increase the molecular space[5].

To produce the biodegradable plastic, microorganisms are used that transform the starch into smaller molecules of lactic acid, which is used as a base for the elaboration of polylactic acid polymer chains. The cross-linking of PLA chains results in biodegradable plastic sheets that serve as the basis for the manufacture of many biodegradable plastic products that can then be injected, extruded and thermoformed as is done with petroleum-based plastics.

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In conclusion, bioplastics are finding an increasing number of applications thanks to the development of new materials and the improvement of their mechanical properties, which is also making production costs cheaper and solving many problems related to their manufacture, so they are gaining more and more followers to implement them as substitutes for conventional plastics of fossil origin, because they can be made with biomass from vegetable waste, a raw material that is considered renewable.

I hope that this description helps to clarify the concept of bioplastic, and allows to differentiate it from biodegradable plastic, since many times the terms are used interchangeably.

There are currently many lines of research underway that seek to transform plants, plant debris and algae into more sustainable biodegradable plastics, perhaps not all of them will come to fruition and only a few will prove to be technically and economically viable, so time will tell if bioplastics will be the definitive alternative to conventional plastics.

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## Referencias

  1. Malajovich, M. Guía de actividades. [Biotecnología: enseñanza y divulgación.](www.bteduc.bio.br)
2. ZEAplast (2012). [Cronología de los bioplásticos](www.zeaplast.cl/plasticos-biodegradables/historia-de-los-bioplasticos++-20)
3. Etigo. (2019). [Poliamida 11.](https://www.etigo.fr/es/blog/p-poliamida-11)
4. Wikipedia.com. [Plástico biodegradable](https://es.wikipedia.org/wiki/Pl%C3%A1stico_biodegradable)
5. García, A. (2015). Obtención de un polímero a partir del almidón de maíz. El Salvador.
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