Engineered biosynthesis of biodegradable polymers

Abstract

Advances in science and technology have resulted in the rapid development of biobased plastics and the major drivers for this expansion are rising environmental concerns of plastic pollution and the depletion of fossil-fuels. This paper presents a broad view on the recent developments of three promising biobased plastics, polylactic acid (PLA), polyhydroxyalkanoate (PHA) and polybutylene succinate (PBS), well known for their biodegradability. The article discusses the natural and recombinant host organisms used for fermentative production of monomers, alternative carbon feedstocks that have been used to lower production cost, different metabolic engineering strategies used to improve product titers, various fermentation technologies employed to increase productivities and finally, the different downstream processes used for recovery and purification of the monomers and polymers.

Cloning and Heterologous Expression of Lactate Dehydrogenase Genes from Acid-Tolerant <i>Lactobacillus acetotolerans</i> HT

“…LAB, the major producer of LA, constitutes an important industrial microorganism. In LA fermentation, LAB is required to have high acid tolerance because low pH due to LA production inhibits the cell growth of bacteria (Jambunathan and Zhang, 2016). Lb.…”

“…However, as industrial chemical synthesis leads to the production of racemic LA (Datta et al, 1995), the demand for optically pure isomers produced by fermentation has increased. There are considerably fewer reports on D-LA production than on L-LA production because of the small number of D-LA producers (Zhou et al, 2003;Singhvi et al, 2013;Jambunathan and Zhang, 2016). As the cell growth of bacteria, even LAB, is inhibited by the LA produced, most bacteria cannot produce lactic acid at pH below 4 owing to having low tolerance to acid (Adachi et al, 1998;Jambunathan and Zhang, 2016).…”

“…There are considerably fewer reports on D-LA production than on L-LA production because of the small number of D-LA producers (Zhou et al, 2003;Singhvi et al, 2013;Jambunathan and Zhang, 2016). As the cell growth of bacteria, even LAB, is inhibited by the LA produced, most bacteria cannot produce lactic acid at pH below 4 owing to having low tolerance to acid (Adachi et al, 1998;Jambunathan and Zhang, 2016). Accordingly, it is preferable to employ acid-resistant bacterial strains for effective production of LA.…”

Future trends in synthetic biology in Asia

“…Synthetic biology research also seeks to reduce the generation, and improve the recyclability, of waste. For example, as an alternative material to the fossil fuel‐based conventional plastics, biodegradable polymers can be produced through microbial fermentation, 158,159 such as polylactic acid (PLA), polybutylene succinate (PBS) and polyhydroxyalkanoates (PHA). Choi et al summarized key technology advancements in microbial production of a number of PHA monomers, including feedstock, host organisms, enzymes and metabolic pathways 160 .…”

Enhancement of lactate fraction in poly(lactate-<i>co</i>-3-hydroxybutyrate) synthesized by <i>Escherichia coli</i> harboring the D-lactate dehydrogenase gene from <i>Lactobacillus acetotolerans</i> HT

“…producible from renewable resources and have excellent properties, such as transparency (Jambunathan and Zhang, 2016). PLAs are normally synthesized by chemical processes using heavy metal catalysts (Garlotta, 2001).…”