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The present study is aimed to develop a microbial system for efficient naphthalene bioremediation. A phytotoxicity study was carried out to check the naphthalene detoxification efficiency of Pseudomonas sp. strain SA3 in mung bean (Vigna radiata). For this, administration of the degraded product (supernatant) of 500 mg L

Pollution caused by polycyclic aromatic hydrocarbons (PAHs) is considered a threat to the environment as it is toxic, carcinogenic, and mutagenic, affecting almost every living organism and its surroundings. PAH toxicity increases as their molecular weight rises. Due to their hydrophobic nature, such recalcitrant hydrocarbons settle down in the coastal environment. The marine ecosystem is severely affected by the toxicity created by various PAHs as it has become one of the main reservoirs of petroleum hydrocarbons. Sources of hydrocarbon contamination are discharge from petroleum industries, transportation of oil through ships, accidental oil spills, and dismantling ships at the shore, which allow the PAHs to enter the oceans and contaminate the coastal region. The adverse effect of PAHs not only kill marine organisms, but the PAHs also enter the food chain, which can cause severe health issues in humans. So, there is a constant need to remediate contaminated marine ecosystems. PAH remediation procedures employing physical and chemical modes are being used to ensure PAH-free surroundings. However, these solutions and their byproducts themselves come with their own side effects and give rise to new pollutants. Bioremediation is therefore considered a holistic approach to clean up the environment's contaminated areas. Bacteria-mediated degradation is one of the most enticing, effective, and ecofriendly bioremediation approaches. Under this, PAH breakdown occurs using a single microorganism or a consortium that consumes these pollutants as a carbon source and mineralizes these harmful molecules completely or partially into less hazardous forms. Thus, bacterial-based remediation has emerged as a prominent strategy to combat PAH contamination in coastal areas.

The present study aims to escalate the production of prophylactic agent zeaxanthin using a screened potential bacterial isolate. For this purpose, a freshwater bacterium capable of producing zeaxanthin was isolated from Bor Talav, Bhavnagar. The 16S rRNA sequence confirmed the isolate as Arthrobacter gandavensis. The bacterium was also submitted to Microbial Type Culture Collection, CSIR-Institute of Microbial Technology, Chandigarh, India, with the accession number MTCC 25325. The chemo-metric tools were employed to optimise the influencing factors such as pH, temperature, inoculum size, agitation speed, carbon source and harvest time on zeaxanthin yield. Thereafter, 6 parameters were narrowed down to 3 factors and were optimised using the central composite design (CCD) matrix. Maximum zeaxanthin (1.51 mg/g) was derived when A. gandavensis MTCC 25325 was grown under pH 6.0, 1.5% (w/v) glucose and 10% (v/v) inoculum size. A high regression coefficient (R2=0.92) of the developed model indicated the accurateness of the tested parameters. To the best of our knowledge, this is the first report on tailoring the process parameters using chemo-metric optimisation for escalating the zeaxanthin production by A. gandavensis MTCC 25325.

Additional file 1. Table S1. General characteristics of bacterial isolates showing zeaxanthin production. Fig. S1. Sampling location of pigmented bacterial isolates screened for zeaxanthin production.

Sargassum polycystum has a unique morphology, i.e. stoloniferous branches that arise from primary axes. The regeneration ability of these stoloniferous branches as vegetative propagules was investigated to optimize the growth parameters. Pieces of stoloniferous branch (2–3 cm) were subject to a range of salinities (25–50 psu), photoperiods (24,0, 8,16, 10,14, 12,12, 14:10, 16:8 and 0:24 h L:D), irradiance (5, 25 and, 45 μmol photons m−2 s−1) and pH (7, 7.5, 8, 8.5 and 9) for a period of 35 days. The maximum daily growth rate (DGR) was observed under the conditions of: 35 psu salinity (1.18 ± 0.35% day−1), 16:8 L:D photoperiod (0.94 ± 0.08% day−1), 45 μmol photons m−1 s−1 (1.13 ± 0.28% day−1), and pH 7.5 (1.14 ± 0.12% day−1). The vegetative propagules regenerated from stoloniferous branches were found to produce primary laterals (branches) and phyllodes (leaves) which, developed into new thalli, but without a holdfast.

The effect of algalization on paddy yield and its nutrition were analyzed. The application of Leptolyngbya boryana mat in conjunction with different doses of fertilizer (R + A + 75%N, R + A + 100%N, R + 100%N, and R + A + 125%N) was performed in the paddy fields of Andhra Pradesh, India. Leptolyngbya boryana mat acted as a promising metal sequester and demonstrated an elicited photosynthetic activity (2-fold increase in Chl-a), carbohydrate (2-fold increase) and lipid (1.7-fold increase) content (% w/w) after 2-month cultivation. It also displayed proficient metal (ppm) uptake efficiency in the order Ca > Fe > Mg > K > Na > Mn > Zn > Cr. In grains, higher nutrient accumulation for Fe (~2-fold), Mg (~1.5-fold) and Ca (~5-fold), and a significantly higher translocation factor (Tf) in the order Ca > K > Mg were recorded under R + A + 125%N. In essence, algalization substantially improved the overall nutritive quality of the rice grains, especially its iron content.

Carotenoid has gained a reputation amongst researchers for its robust antioxidant capabilities. This review reasons the inevitability of carotenoid for a larger role than just dietary supplements. In an era dominated by chemical or plant-derived carotenoid, bacterial carotenoid provides a compelling forte to be exploited as a promising alternative. Bacteria are amazingly resourceful beings; however, their low carotenoid content makes them undesirable for commercial applications. Here, we have reviewed their applications as a strong prophylactic agent in the health sector with a myriad of applications. Additionally, various measures for augmenting carotenoid yield through new-age technologies, like sequential nutrition starvation, the induction of carotenoid accumulation in microbial cells by employing several stress factors, and the construction of hyper-carotenoid producing strains through genetic engineering for creating proficient producers have been offered. Finally, SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis has been presented to perceive the significance of four major components involved in its commercialisation.

Microalgae are a spring of valuable compounds finding its wide applicability as cosmo-nutraceuticals, a renewable substitute for bioenergy and bioremediation. The present study utilizes Scenedesmus sp. CCNM 1028, freshwater microalgae, to understand the influence of various microalgal growth media, like BG-11, Chu's 10, Bold's basal medium (BBM) and Zarrouk's media (ZM), on the growth and lutein production. Furthermore, two-stage nitrogen starvation studies were carried out using the selected BG-11 media and its effect on the lutein and biochemical parameters of Scenedesmus sp. CCNM 1028 after 0, 6, 9, 15 and 21 days (d) of nitrogen starvation were recorded. Lutein was accumulated till 6d of nitrogen starvation. Additionally, ~3-fold increase of carbohydrate content (%w/w) was observed after 21d of nitrogen starvation with respect to the control. Thus, this study proposes two-stage nitrogen starvation as a capable strategy to cultivate Scenedesmus sp. CCNM 1028 for lutein (6d) and carbohydrate production (21d).

Nutrients are the deciding factors in the biological production of bioactive compounds. Various growth media like BG11, Zarrouk’s and Chu’s 10 were studied for carotenoid production in Synechocystis sp. CCNM 2501. Maximum carotenoid content (dry weight basis) was found in Zarrouk’s medium (ZM, 7.99 mg g −1 ) followed by BG11 (5.13 mg g −1 ). Echinenone content was 4 times higher in ZM (3.81 mg g −1 ) as compared to BG11 (0.95 mg g −1 ) and Chu’s 10 (0.77 mg g −1 ). Being an economical medium, BG11 was selected for carotenoid production. Further, increase in salinity from 0 to 0.2 M in BG11 medium increases total carotenoid content from 5.82 to 7.05 mg g −1 and later it declines to 6.23 mg g −1 (1 M). 3 times more β-carotene is produced at 1 M salinity as compared to control BG11. The variation in carotenoid composition with change in nutrients/salinity can be a good strategy to enhance certain targeted carotenoids.