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Bioprospecting of Lignin Valorization by Microbes and Lignolytic Enzymes for the Production of Value-Added Chemicals
Published in Jitendra Kumar Saini, Surender Singh, Lata Nain, Sustainable Microbial Technologies for Valorization of Agro-Industrial Wastes, 2023
Anamika Sharma, Rameshwar Tiwari, Lata Nain
Despite lignolytic enzymes, whole microbial cell factories were also developed to produce value-added products from lignin (Becker & Wittmann, 2019). Rhodococcus, having an aromatic ring opening β-ketoadipate pathway, can convert lignin-derived aromatic compounds into fatty acids (Li et al., 2019b). The β-ketoadipate pathway transforms lignin-derived aromatic compounds into a precursor for fatty acid synthesis, i.e., acetyl-CoA. Oleaginous fungi Trichosporon cutaneum was also explored to produce lipid from lignin model compounds like 4-Hydroxybenzaldehyde. Polyhydroxyalkanoates (PHAs), often referred to as “carbonosomes,” are the bio-based polymers of hydroxyalkanoic acid and can replace conventional plastic due to its biodegradable nature (Hu et al., 2018). Microbes produce PHAs as energy and carbon reserves under harsh environmental conditions. Few aerobic microbes can produce PHAs from lignin-derived aromatic compounds in five different ways (Li et al., 2019a). p-coumaric acid and ferulic acid derived from lignin have been shown to be converted into protocatechuic acid, followed by acetyl-CoA, and then converted into PHAs. C. basilensis B-8 (Si et al., 2018), Burkholderia strain ISTR5 (Morya et al., 2021), Pseudomonas sp. (Wang et al., 2018), and Pandoraea sp. ISTKB (Kumar et al., 2017) have already been explored to produce PHAs from lignin or lignin-derived chemicals.
PHB Production, Properties, and Applications
Published in Abdullah Al-Mamun, Jonathan Y. Chen, Industrial Applications of Biopolymers and their Environmental Impact, 2020
M.A.K.M. Zahari, M.D.H. Beg, N. Abdullah, N.D. Al-Jbour
Polyhydroxyalkanoates (PHAs) are bacterial polymers that are formed as naturally occurring storage polyesters by a wide range of microorganisms, usually under unbalanced growth conditions [2]. The mechanical properties of PHAs make them suitable replacements for different petrochemically produced plastics, such as polyethylene and polypropylene, but advantageous to these commodity plastics PHAs are completely degradable to carbon dioxide and water through natural microbiological mineralization. PHAs can be produced by biotechnological processes under controlled conditions. A series of PHAs with different monomeric compositions in addition to different physical and chemical properties could be produced by different types of microorganisms [3]. PHAs are considered of high interest because they have some properties similar to synthetic plastics [1]. In addition, the degradation product of PHA is a common intermediate compound in all higher organisms. PHA is nontoxic and biocompatible with animal tissues, and then it is suitable to be used in different surgical applications [1]. The material properties of PHAs are highly dependent on the constituting monomer units and their molecular weights. To date, more than 150 monomer units with different (R)-pending groups have been reported [4, 5]. One of the well known and most studied biodegradable polymer in the PHA family is P(3HB).
Applications of Green Polymeric Nanocomposites
Published in Satya Eswari Jujjavarapu, Krishna Mohan Poluri, Green Polymeric Nanocomposites, 2020
Mukesh Kumar Meher, Krishna Mohan Poluri
Polyhydroxyalkanoates (PHAs) are naturally occurring biodegradable polymers produced by numerous bacteria and generally classified as aliphatic polyesters. PHAs are deposited in the bacterial cell cytoplasm in the form of water-soluble granules which serve as sources of energy and carbon for the microorganism (Reddy et al. 2003, Sudesh et al. 2000). PHAs have a wide spectrum of monomers that enable PHAs with distinctive properties. Depending on the carbon atoms present in the monomeric units, PHAs can be divided into two groups: long chain length (6–14 carbon atoms) PHA and short chain length (3–5 carbon atoms) PHA (Lee 1996). Poly(d-3-hydroxybutyrate) (P3HB) is the most common and intensively studied amongst the PHAs groups (Byun and Kim 2014). Depending on its monomeric units, the thermoplastic PHA polymer material shows extensive mechanical properties ranging from hard plastic material to elastic rubber type material (Verlinden et al. 2007, Ten et al. 2015, Raza et al. 2018).
Microalgae and bio-polymeric adsorbents: an integrative approach giving new directions to wastewater treatment
Published in International Journal of Phytoremediation, 2022
Palak Saket, Mrinal Kashyap, Kiran Bala, Abhijeet Joshi
Poly (hydroxyalkanoate) (PHA) is a naturally obtained biopolymer carrying thermoplastic capacity with easy biodegradability (Lemoigne 1926). It is a carbon storage component accumulated in microorganisms especially in polyphosphate accumulating organisms. These microorganisms convert organic substrates into PHA by consuming polyphosphates in cells under anaerobic conditions. During aerobic conditions, they take up and accumulate PHA as an intracellular substrate (Mino et al.1998). PHB (polyhydroxy butyrate) is a polyester that belongs to the family of PHA. Pierro et al. (2017) conducted a pilot-scale study for the removal of chlorinated hydrocarbons from groundwater using PHB as an electron donor for biological reductive dechlorination. A similar study was conducted by Bankole et al. (2019) for the removal of heavy metals from electroplating wastewater by PHB functionalized carbon nanotubes. CNTs functionalized with polymer showed greater mechanical stability and electrical conductivity as compared to ordinary CNT. The initial concentration of iron (127.5mg/L) was reduced to 23.115mg/L after adsorption from PB-CNTs (Bankole et al.2019).
A research challenge vision regarding management of agricultural waste in a circular bio-based economy
Published in Critical Reviews in Environmental Science and Technology, 2018
Nathalie Gontard, Ulf Sonesson, Morten Birkved, Mauro Majone, David Bolzonella, Annamaria Celli, Hélène Angellier-Coussy, Guang-Way Jang, Anne Verniquet, Jan Broeze, Burkhard Schaer, Ana Paula Batista, András Sebok
Polyhydroxyalkanoates (PHAs) are a group of renewable and biodegradable bio-based polymers (polyesters), produced naturally by bacteria. These are starting to gradually substitute conventional plastics (e.g. polypropylene, low-density polyethylene) presenting similar physicochemical, thermal, and mechanical properties (Kourmentza et al., 2017). Some small scale-units are operating in Europe, but the main PHA production unit is located in China (Tianan company), using maize as feedstock. This brings some sustainability issues, namely in terms of competition with food use, water footprint and economic cost. Therefore, it is important to explore the use of sustainable feedstock for fermentative PHA bioreactors. The production of PHA from waste materials such as sugar molasses (Carvalho et al., 2014), olive oil mill wastewater (Hilliou, Machado, et al., 2016) or cheese whey (Hilliou, Teixeira, et al., 2016), has been successfully tested. Furthermore, VFAs, such as acetate and butyrate, have been described as efficient feedstock for PHA production by photosynthetic mixed cultures (Fradinho, Oehmen and Reis, 2014). Therefore, VFA-rich residue streams from two step AD could be purified and functionalised into bi-functional monomers for bio-polymers or further converted into biodegradable PHAs by innovative photo-fermentation processes (Fradinho, Oehmen and Reis, 2014). The latter can offer the advantage of saving energy (because no aeration is required) and has the potential for further decrease PHA cost (see previous section, Challenge II).
A New Method for the Production of Polyhydroxyalkanoates by Bacillus sp. and Detect the Presence of PHA Synthase
Published in Smart Science, 2018
Sasikala Sadasivam, Santhosh Sigamani, Hemalatha Venkatachalam, Dhandapani Ramamurthy
The accumulation of plastic waste generated by petrochemical industries in the environment has become a major issue. Researchers have developed an alternative, fully biodegradable plastics, such as polyhydroxyalkanoates (PHAs). The PHA extracted from bacterial cells shows properties similar to polypropylene [1]. PHAs are water insoluble, they get accumulated in intracellular granules within the cells. It is highly beneficial for bacteria to accumulate excess nutrients inside in the cells, as their general physiological is not affected. By polymerization of soluble intermediates to insoluble molecules, the cell does won’t undergo changes in its osmotic state. Hence, release of the valuable compounds from the cell is prevented and the availability of nutrients will be securely available at a cost-effective maintenance [2]. The worldwide concern is about the development of biodegradable plastic materials as a remedy towards harmful effects caused by plastic wastes on the environment. These chemically synthesized materials by polymerization, contribute towards air pollution and problems related to waste management. The fear of depletion of wood resources has established plastics as the material of choice in many applications. In food sector, various characteristics of plastics such as low density, ready scalability, unbreakable, appearance, impermeability to oxygen and water vapor, low temperature and flexibility have contributed for its large usage. All this has endorsed worldwide research to develop new biodegradable alternatives to plastic. Biodegradable polymers are a new generation materials that are able to reduce environmental impact in terms of energy consumption and greenhouse effect.