A review on biodegradable polylactic acid (PLA) production from fermentative food waste - Its applications and degradation

Due to its low carbon footprint and environmental friendliness, polylactic acid (PLA) is one of the most widely produced bioplastics in the world. Manufacturing attempts to partially replace petrochemical plastics with PLA are growing year over year. Although this polymer is typically used in high-end applications, its use will increase only if it can be produced at the lowest cost. As a result, food wastes rich in carbohydrates can be used as the primary raw material for the production of PLA. Lactic acid (LA) is typically produced through biological fermentation, but a suitable downstream separation process with low production costs and high product purity is also essential. The global PLA market has been steadily expanding with the increased demand, and PLA has now become the most widely used biopolymer across a range of industries, including packaging, agriculture, and transportation. Therefore, the necessity for an efficient manufacturing method with reduced production costs and a vital separation method is paramount. The primary goal of this study is to examine the various methods of lactic acid synthesis, together with their characteristics and the metabolic processes involved in producing lactic acid from food waste. In addition, the synthesis of PLA, possible difficulties in its biodegradation, and its application in diverse industries have also been discussed.

A crucial review on polycyclic aromatic Hydrocarbons - Environmental occurrence and strategies for microbial degradation

Over the last century, contamination of polycyclic aromatic hydrocarbons (PAHs) has risen tremendously due to the intensified industrial activities like petrochemical, pharmaceutical, insecticides and fertilizers applications. PAHs are a group of organic pollutants with adverse effects on both humans and the environment. These PAHs are widely distributed in various ecosystems including air, soil, marine water and sediments. Degradation of PAHs generally occurs through processes like photolysis, adsorption, volatilization, chemical degradation and microbial degradation. Microbial degradation of PAHs is done by the utilization of diverse microorganisms like algae, bacteria, fungi which are readily compatible with biodegrading/bio transforming PAHs into H₂O, CO₂ under aerobic, or CH₄ under anaerobic environment. The rate of PAHs degradation using microbes is mainly governed by various cultivation conditions like temperature, pH, nutrients availability, microbial population, chemical nature of PAHs, oxygen and degree of acclimation. Several microbial species including Selenastrum capricornutum, Ralstonia basilensis, Acinetobacter haemolyticus, Pseudomonas migulae, Sphingomonas yanoikuyae and Chlorella sorokiniana are known to degrade PAHs via biosorption and enzyme-mediated degradation. Numerous bacterial mediated PAHs degradation methods are studied globally. Among them, PAHs degradation by bacterial species like Pseudomonas fluorescence, Pseudomonas aeruginosa, Rhodococcus spp., Paenibacillus spp., Mycobacterium spp., and Haemophilus spp., by various degradation modes like biosurfactant, bioaugmentation, biostimulation and biofilms mediated are also investigated. In contrarily, PAHs degradation by fungal species such as Pleurotus ostreatus, Polyporus sulphureus, Fusarium oxysporum occurs using the activity of its ligninolytic enzymes such as lignin peroxidase, laccase, and manganese peroxidase. The present review highlighted on the PAHs degradation activity by the algal, fungal, bacterial species and also focused on their mode of degradation.

A critical review on different harvesting techniques for algal based biodiesel production

The fuels retrieved from renewable sources which are usually employed as both carbon and energy sources are termed as neutral based biofuels. The most promising feedstock from renewable sources with great potentiality in contributing to the inclining energy demand is microalgae. These microalgae can be harnessed readily in terms of obtaining qualitative biodiesel with greater energy consumption under limited operational cost. The process of harvesting or dewatering microalgae could be carried under single or sequential combinations of operations. The major drawback of harvesting such as huge operational cost could be lowered by increasing the level of automation than cost of investments. The present review concentrates and explores on the techno-economic analysis of the microalgal harvesting and dewatering processes on a large scale. Along with these advanced techniques enclosing the utilization of nanoparticles for harvesting has also been explored. And it also adds with the impacts of concerning facts on energy consumption, processing cost and recovery of resources during harvesting.

Comparison of integrated sustainable biodiesel and antibacterial nano silver production by microalgal and yeast isolates

Microalgal isolates (Chlorella sp. and Spirulina sp.) and yeast isolates (Candida albicans and Saccharomyces sp.) were employed as the resources of biodiesel production and silver nanoparticle synthesis. The prominent peaks of the FTIR spectrum accustomed the efficient lipid property. The developed profile containing fatty acid methyl ester (FAME) displayed the elevated amount of both saturated (C15:0, C17:0, C21:0) and unsaturated (C17:1, C18:2, C20:4) fatty acids. The physicochemical properties analyzed by using Biodiesel analyzer V1.1.software, confirmed the competency of the isolates for sustainable biodiesel production. Biosynthesis of silvernanoparticles (AgNPs) were accomplished extracellularly by using supernatant of microalgal and yeast culture. The maximum absorbance at 420 and 421 nm under UV-visible spectra showed the presence of nanoparticles. The purity of the synthesized AgNPs were analyzed by XRD analysis. The elemental silver presence was affirmed by EDAX, SEM and AFM, the results revealed spherical crystalline shaped nanoparticles of size ranging from 2.0 to 7.3 nm. The antimicrobial efficacy of the silver nanoparticles (AgNPs) against various clinical pathogens which includes Bacillus sp., E. coli, Klebsiella sp., Proteus sp. and Staphylococcus aureus were observed. However, enhanced antimicrobial activity was displayed by the AgNPs, produced by Candida albicans (12 mm) against Bacillus sp., and E.coli, the nanoparticle produced by Chlorella sp. showed the least antagonistic activity (07 mm).