Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization

Production of Lipopeptide Biosurfactant Using Wastewater from Parboiled Paddy Rice and Evaluation of Antifungal Property of the Biosurfactant Against Two Dermatophyte Fungi

A previously isolated lipopeptide biosurfactant-producing bacterium Bacillus licheniformis SCV1 was investigated for the production of the biosurfactant using wastewater from parboiled paddy rice. The biosurfactant thus produced was evaluated for its antifungal property against dermatophyte fungi Trichophyton ajelloi and Microsporum fulvum. Results revealed that the bacterial strain reduced surface tension of the media from 56.16 ± 1 mN/m to 35 ± 0.9 mN/m within 12 h, which further shrank to 29.3 ± 1 mN/m in 24 h of incubation. The yield of the biosurfactant was 3.15 ± 0.25 g/L at 48 h of incubation. The obtained biosurfactant exhibited efficient emulsifying activity against a wide range of hydrophobic substrates such as crude oil, olive oil, engine oil, and kerosene oil used in the study. The critical micelle concentration of the biosurfactant was found to be 80 mg/L. Structural characterization using FT-IR and TLC revealed that the biosurfactant produced by the strain in the wastewater is a lipopeptide consisting of surfactin and iturin. LCMS analysis revealed that the surfactin homologs range from C12 to C17-surfactin while the iturin contains C13 to C17-iturin homologs. It also revealed an in vitro study that the biosurfactant has antifungal properties against dermatophyte fungi Trichophyton ajelloi and Microsporum fulvum. Microscopic observation of the hyphae of the treated dermatophyte revealed disruption and fissure of the mycelia. The chemical composition of the wastewater revealed that it contains adequate nutritional composition and micronutrients to support bacterial growth. This is the first report that the wastewater of parboiled paddy could be used as a low-cost substrate for the production of lipopeptide biosurfactant, and the biosurfactant could be used for preventing dermatophytes fungi.

Rice mill wastewater management in the era of circular economy

Several nations around the world use rice as their primary food staple because of its tremendous nutritional value. India's expanding population has sparked a proliferation of rice mills as a result of the country's growing rice demand. However, small and medium-scale industries lack adequate facilities for processing effluents and other waste generated. Paddy is typically processed by parboiling, which involves soaking it in water, boiling it with steam, and then drying and milling. Around 1-1.5 L of water is necessary to partially cook 1 kg of unhusked rice, with approximately half of this water being discharged as effluent. Disposal of rice mill effluent (RME) in water bodies or on the land causes severe damage to soil and water. An inclusive examination of diverse approaches for the treatment and stabilization of partially cooked rice milling effluents is provided. Moreover, the document provides a concise overview of contemporary and environmentally friendly technologies for treating RME. Adsorption, electrocoagulation, chemical coagulation, and bioremediation using microbes, plants, and microalgae are all included in these methods. This manuscript discusses the concept of a circular economy, which is focused on enhancing environmental sustainability through the recycling and repurposing of generated waste into raw materials for the creation of new products. In addition, this review aims to focus on the impact of RME on soils and water species and the status of sustainable management at the point of circular economy with RME bioenergy production (bioelectricity, biomethane, and bio-hydrogen).

Kinetic and stoichiometric parameters in the fed-batch bioreactor production of poly(3-hydroxybutyrate) by Bacillus megaterium using different carbon sources

This study investigates the effects of different strategies on poly(3-hydroxybutyrate)-P(3HB) production in a fed-batch bioreactor by Bacillus megaterium using candy industry effluent (CIE), sucrose, and rice parboiled water (RPW) as carbon sources. In biosynthesis, kinetic and stoichiometric parameters of substrate conversion into products and/or cells, productivity, instantaneous, and specific conversion rates were evaluated. The maximum concentration of P(3HB) was 4.00 g.L-1 (77% of the total dry mass) in 42 h of cultivation in minimal medium/RPW added with a carbon source based on CIE, demonstrating that the fed-batch provided an increase of approximately 22% in the polymer concentration and 32% in the overall productivity in relation to medium based on commercial sucrose. Fed-batch cultivation also had the advantage of avoiding the extra time required for inoculum preparation and sterilization of the bioreactor during the batch, which thereby increased the overall industrial importance of the process. Effluents from the candy, confectionery, and/or rice parboiling industries can be used as alternative substrates for P(3HB) production at a low cost.

Sequential anaerobic-aerobic treatment of rice mill wastewater and simultaneous power generation in microbial fuel cell

Microbial fuel cells (MFCs) have attracted widespread interest due to their capability to generate power while treating wastewater. In the present investigation, rice mill wastewater (RMW) was treated in a dual-chamber MFC with a biological cathode (MFCB), in which anaerobic treatment was provided in the anode compartment, and aerobic treatment was enployed in the cathode compartment. The performance was compared with an identical MFC with an abiotic cathode (MFCA). During continuous operation, the hydraulic retention time (HRT) of the anode compartments of both MFCs was kept at 12 h. The maximum volumetric power density obtained in MFCB (379.53 mW/m3) was lower than MFCA (791.72 mW/m3). Similarly, the maximum open-circuit voltage (OCV) and operating voltages were 0.519 V and 0.170 V for MFCB, while for the MFCA, they were 0.774 V and 0.251 V, respectively. The internal resistance of MFCA was 372.34 Ω while the MFCB showed a higher internal resistance of 533.89 Ω. The linear sweep voltammetry and cyclic voltammetry also demonstrated high electrochemical activity in MFCA compared to MFCB. However, MFCB has shown a higher chemical oxygen demand (COD) removal efficiency (96.8%) than MFCA (88.4%) under steady-state conditions. Both anaerobic and aerobic degradation of organic substrates significantly reduced the COD of RMW. Furthermore, the absence of an expensive catalyst in the cathode substantially reduces the cost of the system. The electrical performance of the system can be enhanced by employing novel cathode material with surface modification.

Influence of redox potential on the accumulation of poly(3-hydroxybutyrate) by Bacillus megaterium

The main goal of the present study was to evaluate the oxidation-reduction potential (ORP) on the production of poly(3-hydroxybutyrate) (P(3HB)) by Bacillus megaterium. Each microorganism has an optimal ORP range, and changes to the culture medium's ORP may redistribute the cell's metabolic flux, as such, the measurement and control of the ORP profile allows one to, in a way, manipulate the microbial metabolism, affecting the expression of certain enzymes and allowing for better control over the fermentative process. The ORP tests were carried out in a fermentation vessel coupled with an ORP probe, containing 1 L of mineral medium added with agroindustry byproducts (60% v/v of confectionery wastewater, and 40% v/v of rice parboiling water). The system's temperature was kept at 30 °C, with an agitation speed of 500 rpm. The vessel's airflow rate was controlled via a solenoid pump based on the ORP probe's data. Different ORP values were evaluated to verify their impact on biomass and polymer production. Cultures using OPR levels of 0 mV displayed the highest amounts of total biomass (5.00 g L^-1) when compared to - 20 mV and - 40 mV (2.90 g L^-1 and 0.53 g L^-1, respectively). Similar results were also found for P(3HB)-to-biomass ratio, with polymer concentration being reduced when using ORP levels below 0 mV and with a maximum amount of polymer-to-biomass ratio of 69.87% after 48 h of culture. Furthermore, it was possible to observe that the culture's pH can also affect total biomass and polymer concentration, albeit to a lesser extent. Thus, when considering the data found during this study, it is possible to observe that ORP values can greatly impact B. megaterium cell's metabolism. Furthermore, the measurement and control of ORP levels may be an invaluable asset when trying to maximize polymer production under different culture conditions.

Recent updates to microbial production and recovery of polyhydroxyalkanoates

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum.

Roles of microalgae-based biofertilizer in sustainability of green agriculture and food-water-energy security nexus

For years, agrochemical fertilizers have been used in agriculture for crop production. However, intensive utilization of chemical fertilizers is not an ecological and environmental choice since they are destroying soil health and causing an emerging threat to agricultural production on a global scale. Under the circumstances of the increasing utilization of chemical fertilizers, cultivating microalgae to produce biofertilizers would be a wise solution since desired environmental targets will be obtained including (1) replacing chemical fertilizer while improving crop yields and soil health; (2) reducing the harvest of non-renewable elements from limited natural resources for chemical fertilizers production, and (3) mitigating negative influences of climate change through CO₂ capture through microalgae cultivation. Recent improvements in microalgae-derived-biofertilizer-applied agriculture will be summarized in this review article. At last, the recent challenges of applying biofertilizers will be discussed as well as the perspective regarding the concept of circular bio-economy and sustainable development goals (SDGs).

Recycling of wet grinding industry effluent using effective Microorganisms™ (EM)

A considerable volume of effluent released from the food processing industries, after the extensive use in the products manufacturing and industrial process. Effluents, either without treatment or with improper treatment, released out from the industries would severely damage the environment and human health. An investigation was done by recycling the effluent samples, collected from the wet grinding industry, Madurai, India, which was determined with an acidic pH (5.93), high turbidity (160.78 NTU), high BOD (62.4 mg/l) and COD (274.38 mg/l) and a significantly higher quantity of starch (115.81 mg/l). Biological wastewater treatment method was chosen in this experiment on the basis of the biodegradability index of effluent (3.21-10.75). The main goal of this study was to evaluate the effectiveness of wastewater treatment in a prototype STP utilizing the Effective Micro-organisms™ Consortium application. The US EPA International Water Quality Standards and the Water Quality Index were used to compare the water quality of the recycled effluent with and without the EM application. The effluent from the EM consortium treatment was found to have acceptable levels of pH (7.38), salinity (1.94 ppt) and Conductivity (4.05 mS); and a declining trend found in TDS (1.81 ppt), BOD (24.4 mg/l) and COD (148.83 mg/l) level when the effluent treated using EM. Removal effectiveness of EM significant reduce in the treated effluents starch (85.15%), sulphate (78.42), phosphate (79.60), nitrogen (65.54%), and turbidity (82.73%) level were observed. Which was shown to be comparatively better than employing without EM treatment. This research substantially intends to the best practices, towards sustainable industries through Cleaner Production Mechanism.

A techno-economic assessment of nutrient recovery from wastewater using microalgae: scenario in India collected from published literature

The true potential of the microalgae-based wastewater treatment (MWT) process is determined based on whether the process will provide a positive energy output and whether it is economically viable. The objectives of this study are dynamic modelling of microalgae growth based on initial wastewater concentration, temperature, solar radiation and a techno-economic assessment for an MWT scheme for application in a hot, dry climate. Through reference to relevant literature data on MWT in the Indian subcontinent, a selection of appropriate microalgal species Chlorella and Scenedesmus was made. The dynamic model developed was successfully calibrated and validated using independent experimental data collected from the published literature. Cost of production of bio-crude from microalgae grown in a hybrid photobioreactor and pond system in kitchen wastewater of Indian Institute of Technology, Hyderabad was calculated. A break-even selling price (BESP) of US$0.549/kg was obtained for the microalgae biomass. The cost of production of 1 L bio-crude was US$0.96 (Rs 69-74), which is comparable with crude oil cost. The model developed can be used by practising engineers to predict biomass growth and nutrient removal, thereby achieving a break-even point for cost efficiency.

Environmental impacts of hazardous waste, and management strategies to reconcile circular economy and eco-sustainability

The rise in living standards and the continuous development in the global economy led to the depletion of resources and increased waste generation per capita. This waste might posture a significant threat to human health or the environmental matrices (water, air, soil) when inadequately treated, transported, stored, or managed/disposed of. Therefore, effective waste management in an economically viable and environmentally friendly way has become meaningful. Prominent technology is the need of the day for circular economy and sustainable development to reduce the speed of depletion in resources and produce an alternative means for the future demands in the different sectors of science and technology. In order to meet the potential requirements for energy production or producing secondary raw material, solid waste may be the prime source. The activities of living organisms convert waste products in one form or another in which electronic waste (e-waste) is a modern-day problem that is growing by leaps and bounds. The disposal protocols of the e-waste management need to be given proper attention to avoid its hazardous impacts. The e-waste is obtained from any equipment or devices that run by electricity or batteries like laptops, palmtops, computers, televisions, mobile phones, digital video discs (DVD), and many more. E-waste is one of the rapidly growing causes of world pollution today. Plenty of research is available in the scientific literature, which shows different approaches being set up and followed to manage and dispose of waste products. These strategies to manage waste products designed by the states all over the globe revolves around minimal production, authentic techniques for the management of waste produced, reuse and recycling, etc. The virtual survey of the available literature on waste management shows that it lacks specificity regarding the management of waste products parallel to ecological sustainability. The presented review covers the sources, potential environmental impacts, and highlights the importance of waste management strategies to provide the latest and updated knowledge. The review also put forward the countermeasures that need to be taken on national and International levels addressing the sensitive issue of waste management.

Comprehensive review of water management and wastewater treatment in food processing industries in the framework of water-food-environment nexus

Food processing is among the greatest water-consuming industries with a significant role in the implementation of sustainable development goals. Water-consuming industries such as food processing have become a threat to limited freshwater resources, and numerous attempts are being carried out in order to develop and apply novel approaches for water management in these industries. Studies have shown the positive impact of the new methods of process integration (e.g., water pinch, mathematical optimization, etc.) in maximizing water reuse and recycle. Applying these methods in food processing industries not only significantly supported water consumption minimization but also contributed to environmental protection by reducing wastewater generation. The methods can also increase the productivity of these industries and direct them to sustainable production. This interconnection led to a new subcategory in nexus studies known as water-food-environment nexus. The nexus assures sustainable food production with minimum freshwater consumption and minimizes the environmental destructions caused by untreated wastewater discharge. The aim of this study was to provide a thorough review of water-food-environment nexus application in food processing industries and explore the nexus from different aspects. The current study explored the process of food industries in different sectors regarding water consumption and wastewater generation, both qualitatively and quantitatively. The most recent wastewater treatment methods carried out in different food processing sectors were also reviewed. This review provided a comprehensive literature for choosing the optimum scenario of water and wastewater management in food processing industries.

Cereal processing waste, an environmental impact and value addition perspectives: A comprehensive treatise

This review is to describe various methods used for the treatment of cereal processing wastes and their efficiency to reduce environmental issues. Physico-chemical and biological methods have great potential for the treatment of cereal industrial waste. These methods can be used alone or in combination with effective treatment. Physico-chemical treatments are mostly employed for the pretreatment of cereal processing wastes that helps in reduced sludge formation during biological treatments. Biological treatments are mostly used owing to their high efficiency in removing pollutants, and less expensive than physico-chemical treatments. However, these treatments consume more time as compared to physico-chemical treatments. These treatments also proved to be efficient for a high rate of cereal waste conversion into value-added products. Thus, cereal industrial waste can result in value-added products such as biohydrogen, bioethanol, butanol, biogas and biocoal as biofuels, industrial valued enzymes, biomass, biofertilizer, proteins, organic acids, polysaccharides and few others.

Wheat Can Access Phosphorus From Algal Biomass as Quickly and Continuously as From Mineral Fertilizer

Algae can efficiently take up excess nutrients from waterways, making them a valuable resource potentially capable of replacing synthesized and mined fertilizers for agriculture. The capacity of algae to fertilize crops has been quantified, but it is not known how the algae-derived nutrients become available to plants. We aimed to address this question: what are the temporal dynamics of plant growth responses to algal biomass? to better propose mechanisms by which plants acquire nutrients from algal biomass and thereby study and promote those processes in future agricultural applications. Data from various sources were transformed and used to reconstruct the nutrient release from the algae Chlorella vulgaris and subsequent uptake by wheat (Triticum aestivum L.) (as reported in Schreiber et al., 2018). Plants had received 0.1x or 1x dried algae or wet algae, or zero, 0.1x or 1x mineral fertilizer calculated from agricultural practices for P application and grown to 55 days in three soils. Contents of P and other nutrients acquired from algae were as high as from mineral fertilizer, but varied based on moisture content and amount of algae applied to soils (by 55 days after sowing plants with 1x mineral fertilizer and 1x dried algae had 5.6 mg P g DWshoot; 2.2-fold more than those with 0 or 0.1x mineral fertilizer, 0.1x dried algae and wet algae, and 1x wet algae). Absolute and relative leaf area growth and estimated P uptake rates showed similar dynamics, indicating that wheat acquires P from algae quickly. A model proposes that algal fertilizer promotes wheat growth after rapid transformation in soil to inorganic nutrients. We conclude theoretically that phosphorus from algal biomass is available to wheat seedlings upon its application and is released gradually over time with minor differences related to moisture content on application. The growth and P uptake kinetics hint at nutrient forms, including N, and biomass stimulation worthy of research to further exploit algae in sustainable agriculture practices. Temporal resolved phenotype analyses in combination with a mass-balance approach is helpful for understanding resource uptake from recycled and biofertilizer sources by plants.

Phosphorus removal from landfill leachate by microalgae

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Microalgae were able to grow in high N-NH₄⁺ landfill leachate

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P-PO₄⁻³ removal was quicker than N-NH₄⁺ and N-NO₃

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Microalgal species stored P-PO₄⁻³ as intracellular poly-P granules

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100% P-PO₄⁻³ was removed before reaching the end of experiment

Phosphorus is an essential constituent of all living organisms but it is non-renewable and its natural reserves are fast depleting. Phosphorus discharged in wastewater could be sustainably reused by microalgae. Knowledge about cellular phosphorus dynamics in microalgae has been rapidly advancing and luxury phosphorus (poly-P) uptake phenomenon by microalgae is becoming the focus point for many research studies. Ultra-membrane treated landfill leachate was used as a nutrient medium for the growth of indigenous microalgal species with simultaneous removal of phosphorus (P-PO₄⁻³) and nitrogen (N-NH₄⁺ and N-NO₃). Different concentrations of phosphorus (15–100 mg. L^-1 P-PO₄⁻³) was added to leachate. Highest nitrogen removal (69.03% N-NH₄⁺) was observed for 100 mg. L^-1 P-PO₄⁻³ supplemented medium. P removal efficiency was 100% for all the tested P-PO₄^-3 concentrations. Intracellular poly-P was detected by florescence microscopy. Microalgae can be grown and utilized for the sustainable recovery of P and N from landfill leachate.

Phycoremediation of paddy-soaked wastewater by indigenous microalgae in open and closed culture system

Phycoremediation; biotransformation of nutrients and or pollutants by microalgae, supports sustainable wastewater treatment, coupled with biomass production, resulting in enhanced cost savings, waste minimization, and energy conservation. A major challenge in this technique involves cultivation system to be adopted, mode of treatment and harvesting methods. Three different algal cultivation systems; polybags (PB), photobioreactors (PBR) and race way ponds (RWP) were employed for culturing an indigenous microalga, Scenedesmus obliquus in rice mill paddy-soaked wastewater (PSW). The maximum biomass productivity (BP) of 340 ± 2 mg/L/d was observed in PBR with an ammonical nitrogen (NH₃-N) removal (R_N) of 96.12 ± 0.21% and the phosphates (PO₄-P) removal (R_P) of 97.58 ± 0.18%. Highest lipids (L)∼12% (% biomass), protein (P)∼40% and carbohydrates (C)∼20%) were gained in PBR culture system, followed by RWP and PB.

Microwave Parboiling: Reduction in Process Time, Browning of Rice and Residual Phosphorus Content in the Waste Water

The conventional prolonged parboiling process results in high operation cost and grain darkening, which may limit consumption. Moreover, residue generation by rice industries is another challenge. The objective of this study was to evaluate the use of microwave irradiation during soaking and gelatinization stages of parboiling rice. Processing time, colorimetric profile, broken and nongelatinized grains, sucrose and glucose content, free 5-hydroxymethyl-2-furfural, and residual phosphorus were evaluated. As the soaking and gelatinization times during microwave treatments increased, the colorimetric parameters increased; however, the values were lower than those with the conventional process. Regardless of soaking time, a decrease in broken and nongelatinized grains was obtained by using the lowest steaming time (5 min). Additionally, lower residual phosphorus content was found in soaking water (10 and 20 min) when using microwave irradiation. Under favorable conditions, a reduction in the levels of broken and nongelatinized grains, residual phosphorus, and color changes was observed, indicating that microwave irradiation may be more beneficial than conventional parboiling. PRACTICAL APPLICATION: Parboiling requires a high volume of water and soaking time, which leads to high costs, underutilization of infrastructures, and high residue in the water after processing. The rapid parboiling process involves the use of microwaves during the soaking and gelatinization stages. The main advantages of the microwave parboiling process include reduced processing time, ranging from 83% to 95%, higher gelatinization, greater yield, reduced darkening, and reduced residual phosphorus in the effluents by 60%. This report can aid industries in streamlining their processes, thereby providing a high-quality, lower cost, and environmentally safe product.

Phytotoxicity Evaluation of Wastewater from Rice Parboiling

The aim of this study was to evaluate the phytotoxicity of raw and treated effluents from a parboiling rice industry in the south of Brazil. The evaluation included 19 physicochemical parameters and a phytotoxicity test using lettuce and cucumber seeds as bioindicators. The germination index (GI) of both seeds was decreased when in contact with the raw effluent (p < 0.05) and with the treated effluent reduced the GI of cucumber seeds (p < 0.05) and the root length (RL) of lettuce seeds (p < 0.05). For lettuce seeds exposed to the treated effluent there was a negative correlation (p < 0.05) between RL and Mn (- 0.82) and between GI and Fe (- 0.68). For cucumber seeds in the raw effluent, the Fe showed negative correlation (p < 0.05) with seed germination (- 0.75), but, in the treated effluent, their GI presented positive correlation (0.61) with the ammoniacal-N (p < 0.05). The results indicated that both effluents showed phytotoxicity for lettuce and cucumber seeds.

Economic and sustainable management of wastes from rice industry: combating the potential threats

Rice is one of the imperative staple foods, particularly in the developing countries. The exponential boom in human population has resulted in the continuous expansion in the rice industry in order to meet the food demands. The various stages of paddy processing release huge quantity of solid wastes, mainly rice husk, rice husk ash and liquid wastes in the form of rice industry wastewater. The discharge of the rice industry wastewater imparts a substantial threat to the aquatic bodies and the nearby surrounding and, thus, consequently demands eco-benign treatment plan. As a result, different strategies are needed to enhance the effluent quality and minimize the operational cost of the treatment process. Therefore, efficient technological approach targeting the minimization of pollution as well as assuring the economic prosperity should be implemented. In this review article, several aspects related to the rice industry discussing the significant challenges involved in the generation of both solid and liquid wastes, mitigation experiments and future prospects have been meticulously elaborated. Furthermore, the article also focuses on the various processes utilized for reducing the pollution load and promoting the practice of reuse and recycle of waste rather than the discharge action for the sake of sustainability and the emergence of novel techniques for the generation of energy and value-added products.