Multimillion-dollar plastic waste is the cause of global environmental problems. In Kazakhstan, more than 5 million solid household waste is generated annually, of which plastic is 10-15 %. This is a powerful incentive for the creation of domestic, special, environmentally friendly polymer materials, one of which is poly-3-hydroxybutyrate (PHB) and its copolymers.
They are synthesized in the cells of many soil microorganisms as reserve energy substances. The advantages of PHBs are that they are biocompatible with human tissues, biodegradable, have thermoplasticity, optical activity and antioxidant properties. Bioplastics are in high demand and could become a versatile application product. According to the data presented, PHB materials have a high potential as an eco-alternative to plastics based on petrochemical derivatives.
Plastic production increases geometrically every year. Over the past 50 years, plastic production has increased 22 times, which has led to the allocation of about 180 billion US dollars in the last decade alone. Currently, 80% of all waste in the world is plastic, which cannot be decomposed for a long time (about 100 years).
In this regard, the development of bioplastics by large–scale manufacturers of biodegradable plastics, such as NatureWorks in the USA, Mitsubishi Chemicals in Japan, and BASF and Novamont in Europe, is being updated. The use of biodegradable plastics is showing a trend of rapid growth worldwide. It increases to 27% every year. In addition, the production of biodegradable plastics themselves is only up to 12%.
Microorganisms produce various types of high molecular weight polyhydroxyalkanoates, and among them, PHB is considered the most common. Chemically, such polyesters are repeating hydroxyacyl monomers, while their general formula is [-O-CH(R) –CH2 -CO-] n. The R = CH3 group is important for the commercialization of these biopolyesters because of its characteristics such as biodegradability and thermal stability. The production of bioplastics proceeds in three directions: by synthesis from monomers, by fermentation by microorganisms and by polymerization of lactic acid derivatives as polylactates. Among the biodegradable plastics, various polyesters, glycolic acid, polymers, polyhydroxybutyrate and its fatty acids, etc. can be distinguished. But, nevertheless, the production of environmentally friendly polymers is not much inferior to the production of petroleum-based plastics.
In addition to thermoplasticity, PHBs have optical activity, antioxidant properties, piezoelectric effect and, most importantly, they are characterized by biodegradability and biocompatibility. Notable amounts of PHB accumulate bacteria from the genera: Alcaligenes, Chromatium, Hyphomicrobium, Methylobacterium, Nocardia, Pseudomonas, Rhizobium, Spirillum, Streptomyces. However, only a few microorganisms are promising for industrial biosynthesis of biopolymer: Bacillus, Alcaligenes, Ralstonia, Azotobacter and Methylobacterium. They are able to accumulate polyesters on available substrates.
Project aim is to isolate and identify strains producing polyhydroxybutyrate as a source of biodegradable plastics for household and biomedical purposes.
The results of the research will allow us to deepen knowledge on the management of microbial biosynthesis processes and biosynthesis management in various fields of industry, everyday life and medicine. It has a high probability of commercialization of the resulting polymer composite for biomedical needs. There is no active production of PHB in Kazakhstan, therefore, research in this area is new and highly relevant for our country. To date, the topic of studying this project fully meets the requirements and criteria of the green economy of Kazakhstan and is being studied in many countries. The introduction of microbiological producers will significantly expand the potential of biological research and their application in the industry.
Rysbek A.B. H-index – 1; ResearcherID Q-2325-2017; ORCID 0000-0001-8290-0552; Scopus Author ID 57415916300
Abeldenov S.K. H-index –4; ResearcherID F-5139-2015; ORCID 0000-0002-6974-9138; Scopus Author ID 56674705400
Turgimbayeva A.M. H-index –2; ResearcherID N-6857-2017; ORCID 0000-0001-7263-1643; Scopus Author ID 57202383621
Zhumabaev A.R. H-index –3; ORCID 0000-0001-9022-0741; Scopus Author ID: 57193544703; SciProfiles: 1937315; Loop profile: 1987375
Kirillov S.O. H-index –1; ResearcherID N-6322-2017; ORCID 0000-0001-6229-5762
Shaizadinova A.M. H-index –2; ORCID 0000-0002-5911-3064; Scopus Author ID: 57224822522
2023
5 promising strains of PHB producers were isolated from Lake Kobeytuz, Yerementau district, Akmola region. Their morphological and physiological-biochemical properties were studied. The selected isolates were identified. The design of primers for the amplification of the PHB synthase gene has been prepared.
2024
The cultivation of producers was carried out under optimal ecophysiological conditions using the periodic renewal method for 120 hours (5 days), during which the PHB concentration reached 18.03 g/L by the 72nd hour. As a result of UV irradiation, three producers were obtained from two strains, with colonies exhibiting different structures and shapes. An effective producer was obtained under the influence of abiotic stress factors, including heavy metals (CoCl₂, CuSO₄, FeCl₃, MnCl₂, ZnSO₄·7H₂O), NaCl salt up to 10%, medium acidity (pH 5–9), and temperatures ranging from 20°C to 40°C. The strains demonstrated varying degrees of resistance to external factors. The carbon source utilization profile by PHB producers was investigated. All tested strains showed abundant growth in media containing various carbon sources. Additionally, the effects of various pesticides (metribuzin, thiamethoxam, clopyralid) on the microbial strains were evaluated. Overall, the results suggest that the effect of pesticides depends on both the concentration and the type of strain, which is important to consider when applying these substances.
For the 1st quarter of 2025:
The PHB-producing strain was isolated and confirmed using transmission electron microscopy (TEM), which revealed the presence of more than 10 dense PHB granules per cell. The purity of the extracted polymer was assessed using Fourier-transform infrared spectroscopy (FTIR). The obtained polymer was subsequently used to create a membrane, which was then tested for permeability to water vapor, oxygen, carbon dioxide, and for resistance to biofilm puncture. The resulting PHB-based membrane demonstrated promising barrier properties, indicating its suitability for various industrial applications, including biomedical devices.