Interdisciplinary Centre of Marine and Environmental Research

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Publications

Microalgal-based industry vs. microplastic pollution: Current knowledge and future perspectives

Publication . Mendonça, Ivana; Faria, Marisa; Rodrigues, Filipa; Cordeiro, Nereida

Microalgae can play a crucial role in the environment due to their efficient capture of CO2 and their potential as a solution for a carbon-negative economy. Water quality is critical for the success and profitability of microalgal based industries, and understanding their response to emergent pollutants, such as microplastics (MPs), is essential. Despite the published studies investigating the impact of MPs on microalgae, knowledge in this area remains limited. Most studies have mainly focused on microalgal growth, metabolite analysis, and photosyn thetic activity, with significant discrepancies in what is known about the impact on biomass yield. Recent studies show that the yield of biomass production depends on the levels of water contamination by MPs, making it necessary to reduce the contamination levels in the water. However, present technologies for extracting and purifying water from MPs are limited, and further research and technological advancements are required. One promising solution is the use of bio-based polymer materials, such as bacterial cellulose, which offer biode gradability, cost-effectiveness, and environmentally friendly detoxifying properties. This review summarises the current knowledge on MPs pollution and its impact on the viability and proliferation of microalgae-based industries, highlights the need for further research, and discusses the potential of bio-solutions for MPs removal in microalgae-based industries.

2024Journal article

Open access

Bacterial cellulose biopolymers: the sustainable solution to water-polluting microplastics

Publication . Faria, Marisa; Cunha, César; Gomes, Madalena; Mendonça, Ivana; Kaufmann, Manfred; Ferreira, Artur; Cordeiro, Nereida

Microplastics (MPs) pollution has become one of our time’s most consequential issue. These micropolymeric particles are ubiquitously distributed across all natural and urban ecosystems. Current filtration systems in wastewater treatment plants (WWTPs) rely on non-biodegradable fossil-based polymeric filters whose mainte nance procedures are environmentally damaging and unsustainable. Following the need to develop sustainable filtration frameworks for MPs water removal, years of R&D lead to the conception of bacterial cellulose (BC) biopolymers. These bacterial-based naturally secreted polymers display unique features for biotechnological applications, such as straightforward production, large surface areas, nanoporous structures, biodegradability, and utilitarian circularity. Diligently, techniques such as flow cytometry, scanning electron microscopy and fluorescence microscopy were used to evaluate the feasibility and characterise the removal dynamics of highly concentrated MPs-polluted water by BC biopolymers. Results show that BC biopolymers display removal effi ciencies of MPs of up to 99%, maintaining high performance for several continuous cycles. The polymer’s characterisation showed that MPs were both adsorbed and incorporated in the 3D nanofibrillar network. The use of more economically- and logistics-favourable dried BC biopolymers preserves their physicochemical properties while maintaining high efficiency (93–96%). These polymers exhibited exceptional structural preservation, conserving a high water uptake capacity which drives microparticle retention. In sum, this study provides clear evidence that BC biopolymers are high performing, multifaceted and genuinely sustainable/circular alternatives to synthetic water treatment MPs-removal technologies.

2022Journal article

Open access

Microplastics reduce microalgal biomass by decreasing single-cell weight: the barrier towards implementation at scale

Publication . Mendonça, Ivana; Cunha, César; Kaufmann, Manfred; Faria, Marisa; Cordeiro, Nereida

Microplastics (MPs) are a widespread environmental threat, especially to aquatic and urban systems. Water quality is vital for biomass production in microalgal-based industries. Here, industrially relevant microalgae Tetraselmis suecica, Scenedesmus armatus, and Nannochloropsis gaditana were exposed to PS- and PE-MPs (polystyrene and polyethylene, re spectively – 10-20 μm) contaminated waters (5 and 10 mg/L). Following industrial empirical and ecotoxicological pro cedures, the production period was established as four days (exponential growth phase). 27-long day experiments were conducted to determine the chronic effects of MPs contamination in microalgal biomass yields. MPs induced different responses in cell density: T. suecica decreased (up to 11 %); S. armatus showed no changes; and N. gaditana increased (up to 6 %). However, all three microalgae exhibited significant decreases in biomass production (up to 24, 48, and 52 %, respectively). S. armatus exposed to PS-MPs and N. gaditana exposed to PE-MPs were the most im pacted regarding biomass production. The decrease in biomass yield was due to the reduction in single-cell weight (up to 14, 47, and 43 %), and/or the production of smaller-sized cells (T. suecica). In response to chronic exposure, microalgae showed signs of cell density adaptation. Despite cell density normalizing, biomass production was still re duced compared to biomass production in clean water. Computational modelling highlighted that MPs exposure had a concentration-dependent negative impact on microalgae biomass. The models allow the evaluation of the systematic risks that MPs impose in microalgal-based industries and stimulate actions towards implementing systems to contain/ eliminate MPs contamination in the waters used in microalgae production.

2023Journal article

Open access

Solving urban water microplastics with bacterial cellulose hydrogels: leveraging predictive computational models

Publication . Mendonça, Ivana; Sousa, Jessica; Cunha, César; Faria, Marisa; Ferreira, Artur; Cordeiro, Nereida

The prevalence of microplastics (MPs) in both urban and aquatic ecosystems is concerning, with wastewater treatment plants being considered one of the major sources of the issue. As the focus on developing sustainable solutions increases, unused remnants from bacterial cellulose (BC) membranes were ground to form BC hydrogels as potential bioflocculants of MPs. The influence of operational parameters such as BC:MPs ratio, hydrogel grinding, immersion and mixing time, temperature, pH, ionic strength, and metal cations on MPs flocculation and dispersion were evaluated. A response surface methodology based on experimental data sets was computed to understand how these parameters influence the flocculation process. Further, both the BC hydrogel and the hetero-aggregation of MPs were characterised by UV–Vis, ATR-FTIR, IGC, water uptake assays, fluorescence, and scanning electron microscopy. These highlights that the BC hydrogel would be fully effective at hetero aggregating MPs in naturally-occurring concentrations, thereby not constituting a limiting performance factor for MPs’ optimal flocculation and aggregation. Even considering exceptionally high concentrations of MPs (2 g/ L) that far exceed naturally-occurring concentrations, the BC hydrogel was shown to have elevated MPs floc culation activity (reaching 88.6%: 1.77 g/L). The computation of bioflocculation activity showed high reliability in predicting flocculation performance, unveiling that the BC:MPs ratio and grinding times were the most critical variables modulating flocculation rates. Also, short exposure times (5 min) were sufficient to drive robust particle aggregation. The microporous nature of the hydrogel revealed by electron microscopy is the likely driver of strong MPs bioflocculant activity, far outperforming dispersive commercial bioflocculants like xanthan gum and alginate. This pilot study provides convincing evidence that even BC remainings can be used to produce highly potent and circular bioflocculators of MPs, with prospective application in the wastewater treatment industry

2023Journal article

Open access

Revamping kombucha production: achieving consistency and probiotic potential through a tailor-made microbial consortium

Publication . Fabricio, Mariana Fensterseifer; Vargas, Bruna Krieger; Tischer, Bruna; Wagner, Roger; Ribeiro, Stephanie Reis; Cordeiro, Nereida; Flôres, Simone Hickmann; Záchia Ayub, Marco Antônio

Revising the production of kombucha, this investigation focused on the utilization of a custom-designed starter culture, aiming to establish a consistent, probiotic-rich beverage. A diverse selection of three acetic acid bacteria and two yeast strains was examined to determine the optimal microbial combination. A meticulous examination of the fermentation timeline was undertaken, juxtaposing forced and natural carbonation techniques. A comprehensive analysis encompassing fermentation metabolites, sensory acceptance, volatile compound profiling, and shelf-life testing was executed to ensure the beverage’s superior quality and stability. The resultant probiotic kombucha was produced successfully after 48 h of fermentation with a symbiotic assembly of Koma gataeibacter saccharivorans, Brettanomyces anomala, and Kluyveromyces marxianus. Forced carbonated kombucha exhibited acceptance levels rivaling commercial brands, maintaining an alcohol content consistently beneath the 0.5% (v/v) regulatory standard for a 60-day storage period. Specific esters, namely ethyl 3-methyl butanoate, phenethyl acetate, ethyl hexanoate, and 2-methyl-1-propyl acetate, were identified as key determinants of kombucha flavor profiles. The 90-day shelf-life study indicated a consistent presence of viable probiotic K. marxianus cells in the kombucha. These findings contribute to understanding probiotic Kombucha fermentation and demonstrate the potential for producing a high-quality beverage with desirable sensory characteristics through a custom-designed microbial consortium.

2023Journal article

Open access