Lichen-Associated Bacterium, a Novel Bioresource of Polyhydroxyalkanoate (PHA) Production and Simultaneous Degradation of Naphthalene and Anthracene

Abstract

Lichens are generally known as self-sufficient, symbiotic life-forms between fungi and algae/ cyanobacteria, and they also provide shelter for a wide range of beneficial bacteria. Currently, bacterial-derived biodegradable polyhydroxyalkanoate (PHA) is grabbing the attention of many researchers as a promising alternative to non-degradable plastics. This study was conducted to develop a new method of PHA production using unexplored lichen-associated bacteria, which can simultaneously degrade two ubiquitous industrial toxins, anthracene and naphthalene. Here, 49 lichen-associated bacteria were isolated and tested for PHA synthesis. During the GC-MS analysis, a potential strain of EL19 was found to be a 3-hydroxyhexanoate (3-HHx) accumulator and identified as Pseudomonas sp. based on the 16S rRNA sequencing. GC analysis revealed that EL19 was capable of accumulating 30.62% and 19.63% of 3-HHx from naphthalene and anthracene, respectively, resulting in significant degradation of 98% and 96% of naphthalene and anthracene, respectively, within seven days. Moreover, the highly expressed phaC gene verified the genetic basis of PHA m c l production under nitrogen starvation conditions. Thus, this study strongly supports the hypothesis that lichen-associated bacteria can detoxify naphthalene and anthracene, store energy for extreme conditions, and probably help the associated lichen to live in extreme conditions. So far, this is the first investigation of lichen-associated bacteria that might utilize harmful toxins as feasible supplements and convert anthracene and naphthalene into eco-friendly 3-HHx. Implementation of the developed method would reduce the production cost of PHA m c l while removing harmful waste products from the environment.

Challenges and Perspectives of Polyhydroxyalkanoate Production From Microalgae/Cyanobacteria and Bacteria as Microbial Factories: An Assessment of Hybrid Biological System

“…This symbiotic interaction helps to reduce wastewater treatment efforts by natural way. A recent study has reported lichen-associated Pseudomonas having the ability to detoxify and utilize naphthalene and anthracene for energy reserve storage and produce PHA with 3-HHx unit up to 30.62 and 19.63% of 3-HHx, respectively (Nahar et al, 2019). The proposed system has consortium of microalgae/cyanobacteria and bacteria as two components so as to utilize resources under both light and dark phase (Figure 3B).…”

Perspective Chapter: Development of Food Packaging Films from Microorganism-Generated Polyhydroxyalkanoates

“…Biodegradable PHAs can be produced by many bacterial species and their different strains [69,96]. Although many bacterial species are capable of producing a variety of biopolymers, only a few have high productivity and high production rate [69,97,98]. Among these bacteria; Wauteria eutropha, Azotobacter spp.…”

“…Among these bacteria; Wauteria eutropha, Azotobacter spp. Bacillus sp., Pseudomonas putida, Pseudomonas fuorescens, P. oleovorans, Ralstonia eutropha, Cupriavidus necator, Burkholderia sp., Halomonas sp., Haloferax sp., Aeromonas sp., Thermus thermophilus, Hydrogenophagobacter, Saxogradanobacteria de Saxogradia Erwinia sp., and recombinant E. coli [80,97,98]. Buhwal et al [99] isolated bacteria that accumulate polyhydroxyalkanoates (PHA) from pulp, paper, and wastewater.…”

Integrated Biorefinery Design with Techno‐Economic and Life Cycle Assessment Tools in Polyhydroxyalkanoates Processing

“…Recently, hybrid methods have been introduced in the upstream processes. Among them, mixotrophic cultivation of microalgae or cyanobacteria has been proven to improve the yield of PHA by two-to ninefold; [118] a photoautotrophic-heterotrophic consortium of cyanobacteria/microalgae and bacteria helps to reduce the wastewater treatment (organic waste from wastewater) efforts naturally; [119] and two-module system (1st module: photoautotrophic cyanobacterial growth to produce substrate; 2nd module: heterotrophic bacteria utilizing substrate made from 1st module for PHA production) can compensate for the low PHA yield production from fast-growing photoautotrophic cultivation. [120] Although these proposed methods demonstrated promising results for PHA production, the evaluation of these methods in the context of environmental aspects was not welldeveloped.…”