Marine diatom algae cultivation in simulated dairy wastewater and biomass valorization.

Liquid byproducts and organic wastes generated from dairy processing units contribute as the largest source of industrial food wastewater. Though bacteria-mediated treatment strategies are largely implemented, a more effective and innovative management system is needed of the hour. Thus, the current study involves the cultivation of centric diatoms, Chaetoceros gracilis, and Thalassiosira weissflogii in simulated dairy wastewater (SDWW) formulated using varying amounts of milk powder with artificial seawater f/2 media (ASW). The results revealed that cell density and biomass productivity were highest in the 2.5% SDWW treatment cultures of both the strains, the maximum being in C. gracilis (7.5 × 106 cells mL - 1; 21.1 mg L-1 day-1). Conversely, the total carotenoid, chrysolaminarin, and phenol content were negatively impacted by SDWW. However, a considerable enhancement in the total lipid content was reported in the 2.5% SDWW culture of both species. Furthermore, the fatty acid profiling revealed that though the total polyunsaturated fatty acid (PUFA) content was highest in the control setups, the total mono polyunsaturated fatty acid (MUFA) content was higher in the 5% SDWW setups (30.66% in C. gracilis and 33.21% in T. weissflogii). In addition to it, in the cultures utilizing energy from external carbon sources provided by SDWW, the biodiesel produced was also enhanced owing to the heightened cetane number. Thus, the current study evidently highlights the organic carbon acquisition potential of marine diatoms with the scope of providing sustainable biorefinery.

Seed biopriming as a promising approach for stress tolerance and enhancement of crop productivity: a review.

Chemicals are used extensively in agriculture to increase crop production to meet the nutritional needs of an expanding world population. However, their injudicious application adversely affects the soil's physical, chemical and biological properties, subsequently posing a substantial threat to human health and global food security. Beneficial microorganisms improve plant health and productivity with minimal impact on the environment; however, their efficacy greatly relies on the application technique. Biopriming is an advantageous technique that involves the treatment of seeds with beneficial biological agents. It exhibits immense potential in improving the physiological functioning of seeds, thereby playing a pivotal role in their uniform germination and vigor. Biopriming-mediated molecular and metabolic reprogramming imparts stress tolerance to plants, improves plant health, and enhances crop productivity. Furthermore, it is also associated with rehabilitating degraded land, and improving soil fertility, health and nutrient cycling. Although biopriming has vast applications in the agricultural system, its commercialization and utilization by farmers is still in its infancy. This review aims to critically analyze the recent studies based on biopriming-mediated stress mitigation by alteration in physiological, metabolic and molecular processes in plants. Additionally, considering the necessity of popularizing this technique, the major challenges and prospects linked to the commercialization and utilization of this technique in agricultural systems have also been discussed. © 2023 Society of Chemical Industry.

Response of varying combined nutrients on biomass and biochemical composition of marine diatoms Chaetoceros gracilis and Thalassiosira weissflogii.

Marine diatoms have high adaptability and are known to accumulate lipids under nutrient stress conditions. The present study involves determining the effect of varying macro and micronutrients on growth kinetics and metabolite production of oleaginous marine diatoms, Thalassiosira weissflogii and Chaetoceros gracilis. The results highlighted that C. gracilis and T. weissflogii showed maximum biomass yield of 0.86 ± 0.06 g/L and 0.76 ± 0.01 g/L in the 2f and f supplemented medium respectively. A 2.5-fold increase in cellular lipid content was recorded in the 2f culture setup of both strains ranging from 20 % to 26.7 % (w/w). The study also reveals that high eutrophic nutrient media (f, 2f and 4f) triggered biomass productivity as well as total protein and carbohydrate content in both strains. Thus, providing a reproducible insight of trophic flexibility of diatoms, concomitant with the increment in multiple commercially valuable products.

Biomass valorization of agriculture wastewater grown freshwater diatom Nitzschia sp. for metabolites, antibacterial activity, and biofertilizer.

The sustainable utilization of agricultural wastewater is a major global challenge. This study evaluated the impact of agricultural fertilizer on the biomass potential of Nitzschia sp. for metabolite production, antibacterial activity, and slow release biofertilizer. Cultivation of Nitzschia sp. in agriculture wastewater (0.5 mg ml-1) exhibited maximum cell density (12×105 cells ml-1), protein content (10.0 mg g-1), and lipid content (14.96%). Carbohydrate and phenol content increases in a dose-dependent manner with 8.27 mg g-1 and 2.05 mg g-1 at a concentration of 2 mg ml-1 respectively. There was a 2.1-fold increment in chrysolaminarin content. Both gram-negative and gram-positive bacteria were susceptible to the antibacterial activity of the biomass. The effects of using diatom biomass as a biofertilizer were evaluated on the growth of periwinkle plants, which showed significant improvements in leaf development, branching at an early stage, flowering, and a marked increase in shoot length. Diatom biorefinery holds immense potential in addressing agriculture wastewater recycling and sustainable generation of high-value compounds.

Green synthesis of flower shape ZnO-GO nanocomposite through optimized discharge parameter and its efficiency in energy storage device.

Numerous solution-based methods are used to prepare zinc oxide (ZnO) and graphene oxide (GO) nanocomposite (ZnO-GO NCs) such as sol-gel, hydrothermal, and precipitation. These methods require lots of reagents and involve many stages. In this study, a novel one-step solution-based discharge method is used to prepare ZnO-GO NCs through an electrochemical discharge process (ECDP) without the use of any catalyst or toxic chemical reagent. This study focused on analyzing the effects of input parameters on the production rate of ZnO-GO NCs. The experiment was performed by using Taguchi L9 orthogonal array. Materials removal rate (MRR) is considered as output response. The results reveal that voltage is the most significant factor, followed by temperature and duty cycle for obtaining higher MRR. The optimum parameters obtained from the Minitab software for higher MRR are 40 V, 30%, and 45 °C. Further, the morphology of the nanoparticles (NCs) produced at optimum parameters is analyzed which shows flower shape NCs with multilayer graphene oxide, confirmed by the FESEM and TEM images. The XRD peak at 11.27° and Raman spectroscopy peak of G and D bands reveal GO formation. The prepared ZnO-GO NCs tested as supercapacitor activity in the KOH solution. At the optimum parameter, the specific capacitance is observed to be 523.4 F/g at 2A/g current density. The NCs electrode shows good cyclic stability, with 86% retention of specific capacitance after 5000 cycles. This study shows a promising future of converting the e-waste product into valuable nanomaterials such as GO and ZnO from used dry cell batteries.

Combating biotic stresses in plants by synthetic microbial communities: Principles, applications and challenges.

Presently, agriculture worldwide is facing the major challenge of feeding the increasing population sustainably. The conventional practices have not only failed to meet the projected needs, but also led to tremendous environmental consequences. Hence, to ensure a food-secure and environmentally sound future, the major thrust is on sustainable alternatives. Due to challenges associated with conventional means of application of biocontrol agents in the management of biotic stresses in agroecosystems, significant transformations in this context are needed. The crucial role played by soil microbiome in efficiently and sustainably managing the agricultural production has unfolded a newer approach of rhizosphere engineering that shows immense promise in mitigating biotic stresses in an eco-friendly manner. The strategy of generating synthetic microbial communities (SynComs), by integrating omics approaches with traditional techniques of enumeration and in-depth analysis of plant-microbe interactions, is encouraging. The review discusses the significance of the rhizospheric microbiome in plant's fitness, and its manipulation for enhancing plant attributes. The focus of the review is to critically analyse the potential tools for the design and utilization of SynComs as a sustainable approach for rhizosphere engineering to ameliorate biotic stresses in plants. Furthermore, based on the synthesis of reports in the area, we have put forth possible solutions to some of the critical issues that impair the large-scale application of SynComs in agriculture.

Management of abiotic stresses by microbiome-based engineering of the rhizosphere.

Abiotic stresses detrimentally affect both plant and soil health, threatening food security in an ever-increasing world population. Sustainable agriculture is necessary to augment crop yield with simultaneous management of stresses. Limitations of conventional bioinoculants have shifted the focus to more effective alternatives. With the realization of the potential of rhizospheric microbiome engineering in enhancing plant's fitness under stress, efforts have accelerated in this direction. Though still in its infancy, microbiome-based engineering has gained popularity because of its advantages over the microbe-based approach. This review briefly presents major abiotic stresses afflicting arable land, followed by an introduction to the conventional approach of microbe-based enhancement of plant attributes and stress mitigation with its inherent limitations. It then focuses on the significance of the rhizospheric microbiome and possibilities of harnessing its potential by its strategic engineering for stress management. Further, success stories related to two major approaches of microbiome engineering (generation of synthetic microbial community/consortium, and host-mediated artificial selection) pertaining to stress management have been critically presented. Together with bringing forth the challenges associated with the wide application of rhizospheric microbiome engineering in agriculture, the review proposes the adoption of a combinational scheme for the same, bringing together ecological and reductionist approaches for improvised sustainable agricultural practices.