Polyelectrolyte complexes based on a novel and sustainable hemicellulose-rich lignosulphonate for drug delivery applications.

Polyelectrolyte complexes (PECs) are polymeric structures formed by the self-assembly of oppositely charged polymers. Novel biomaterials based on PECs are currently under investigation as drug delivery systems, among other applications. This strategy leverages the ability of PECs to entrap drugs under mild conditions and control their release. In this study, we combined a novel and sustainably produced hemicellulose-rich lignosulphonate polymer (EH, negatively charged) with polyethyleneimine (PEI) or chitosan (CH, positively charged) and agar for the development of drug-releasing PECs. A preliminary screening demonstrated the effect of several parameters (polyelectrolyte ratio, temperature, and type of polycation) on PECs formation. From this, selected formulations were further characterized in terms of thermal properties, surface morphology at the microscale, stability, and ability to load and release methylene blue (MB) as a model drug. EH/PEI complexes had a more pronounced gel-like behaviour compared to the EH/CH complexes. Differential scanning calorimetry (DSC) results supported the establishment of polymeric interactions during complexation. Overall, PECs' stability was positively affected by low pH, ratios close to 1:1, and the addition of agar. PECs with higher EH content showed a higher MB loading, likely promoted by stronger electrostatic interactions. The EH/CH formulation enriched with agar showed the best sustained release profile of MB during the first 30 h in a pH-dependent environment simulating the gastrointestinal tract. Overall, we defined the conditions to formulate novel PECs based on a sustainable hemicellulose-rich lignosulphonate for potential applications in drug delivery, which promotes the valuable synergy between sustainability and the biomedical field.

Prospects of integrating algae technologies into landfill leachate treatment.

Landfilling of municipal waste, an environmental challenge worldwide, results in the continuous formation of significant amounts of leachate, which poses a severe contamination threat to ground and surface water resources. Landfill leachate (LL) is generated by rainwater percolating through disposed waste materials and must be treated effectively before safe discharge into the environment. LL contains numerous pollutants and toxic substances, such as dissolved organic matter, inorganic chemicals, heavy metals, and anthropogenic organic compounds. Currently, LL treatment is carried out by a combination of physical, chemical, and microbial technologies. Microalgae are now viewed as a promising sustainable addition to the repertoire of technologies for treating LL. Photosynthetic algae have been shown to grow in LL under laboratory conditions, while some species have also been employed in larger-scale LL treatments. Treating leachate with algae can contribute to sustainable waste management at existing landfills by remediating low-quality water for recycling and reuse and generating large amounts of algal biomass for cost-effective manufacturing of biofuels and bioproducts. In this review, we will examine LL composition, traditional leachate treatment technologies, LL toxicity to algae, and the potential of employing algae at LL treatment facilities. Emphasis is placed on how algae can be integrated with existing technologies for biological treatment of LL, turning leachate from an environmental liability to an asset that can produce value-added biofuels and bioproducts for the bioeconomy.

Biochemical conversion of sweet sorghum bagasse to succinic acid.

Succinic acid, an important intermediate in the manufacture of plastics and other commodity and specialty chemicals, is currently made primarily from petroleum. We attempted to biosynthesize succinic acid through microbial fermentation of cellulosic sugars derived from the bagasse of sweet sorghum, a renewable feedstock that can grow in a wide range of climates around the world. We investigated pretreating sweet sorghum bagasse (SSB) with concentrated phosphoric acid at mild conditions (40-85°C) at various residence times and biomass concentrations. We then subjected the pretreated SSB to enzymatic hydrolysis with a commercial cellulase to release glucose. The highest glucose yield was obtained when SSB was pretreated at 50°C for 43 min at 130 g/L biomass concentration on dry basis. Fermentation was carried out with Actinobacillus succinogenes 130Z, which readily converted 29.2 g/L of cellulosic glucose to 17.8 g/L of succinic acid in a 3.5-L bioreactor sparged with CO2 at a rate of 0.5 vvm, thus reducing the carbon footprint of the process. Overall, we demonstrated, for the first time, the use of SSB for production of succinic acid using practices that lower energy use, future equipment cost, waste generation, and carbon footprint.

Study of landfill leachate as a sustainable source of water and nutrients for algal biofuels and bioproducts using the microalga Picochlorum oculatum in a novel scalable bioreactor.

High water demand is a major challenge for the algae industry, so cultivating algae in wastewater can have the double benefit of biomass production and water remediation. The use of landfill leachate (LL), which is wastewater generated in landfills, was investigated to grow the microalga Picochlorum oculatum in a novel horizontal bioreactor (HBR), a low-cost modular cultivation system that reduces water evaporation and contamination risk thanks to its enclosed design. Pilot-scale (150 L) and commercial-scale (2000 L) HBRs that were operated outdoors in Florida using LL in batch and semi-continuous modes generated high cell density cultures (1.7·109 cells mL-1) and reached up to 1.9 g L-1 of dry biomass suitable for biofuel production. Demonstrating the ability of ample non-potable water sources, such as LL, to support algae cultivation is essential for improving the sustainability and cost-effectiveness of commercial algal biofuels and bioproducts, as freshwater resources become increasingly scarce.

A novel horizontal photobioreactor for high-density cultivation of microalgae.

Microalgae are a promising source of biofuels and bioproducts, as they consume CO2 to grow, multiply quickly, and can be cultivated in wastewater and on marginal land. Development of low-cost and high-efficiency microalgal cultivation systems is important to the cost-competitiveness of algae. A floating horizontal photobioreactor (HBR) was developed that is inexpensive and scalable, as it is manufactured from inexpensive plastic film and is modular. Its performance was successfully tested using the marine microalgae Nannochloris atomus Butcher CCAP 251/4A in a 65-L prototype unit. High biomass concentration of 4.0 g L(-1) and productivity of 12.9 g m(-2)d(-1) was achieved indoors under artificial illumination of 31.3 klux (435 µmol m(-2)s(-1)). Outdoors, during semi-continuous operation in Florida, the HBR achieved over the course of 165 days a maximum biomass concentration of 4.3 g L(-1) and an average biomass productivity of 18.2 g m(-2)d(-1) without any contamination issues.

Biotechnological production of ethanol from renewable resources by Neurospora crassa: an alternative to conventional yeast fermentations?

Microbial production of ethanol might be a potential route to replace oil and chemical feedstocks. Bioethanol is by far the most common biofuel in use worldwide. Lignocellulosic biomass is the most promising renewable resource for fuel bioethanol production. Bioconversion of lignocellulosics to ethanol consists of four major unit operations: pretreatment, hydrolysis, fermentation, and product separation/distillation. Conventional bioethanol processes for lignocellulosics apply commercial fungal cellulase enzymes for biomass hydrolysis, followed by yeast fermentation of resulting glucose to ethanol. The fungus Neurospora crassa has been used extensively for genetic, biochemical, and molecular studies as a model organism. However, the strain's potential in biotechnological applications has not been widely investigated and discussed. The fungus N. crassa has the ability to synthesize and secrete all three enzyme types involved in cellulose hydrolysis as well as various enzymes for hemicellulose degradation. In addition, N. crassa has been reported to convert to ethanol hexose and pentose sugars, cellulose polymers, and agro-industrial residues. The combination of these characteristics makes N. crassa a promising alternative candidate for biotechnological production of ethanol from renewable resources. This review consists of an overview of the ethanol process from lignocellulosic biomass, followed by cellulases and hemicellulases production, ethanol fermentations of sugars and lignocellulosics, and industrial application potential of N. crassa.

Bioconversion of dilute-acid pretreated sorghum bagasse to ethanol by Neurospora crassa.

Bioethanol production from sweet sorghum bagasse (SB), the lignocellulosic solid residue obtained after extraction of sugars from sorghum stalks, can further improve the energy yield of the crop. The aim of the present work was to evaluate a cost-efficient bioconversion of SB to ethanol at high solids loadings (16 % at pretreatment and 8 % at fermentation), low cellulase activities (1-7 FPU/g SB) and co-fermentation of hexoses and pentoses. The fungus Neurospora crassa DSM 1129 was used, which exhibits both depolymerase and co-fermentative ability, as well as mixed cultures with Saccharomyces cerevisiae 2541. A dilute-acid pretreatment (sulfuric acid 2 g/100 g SB; 210 °C; 10 min) was implemented, with high hemicellulose decomposition and low inhibitor formation. The bioconversion efficiency of N. crassa was superior to S. cerevisiae, while their mixed cultures had negative effect on ethanol production. Supplementing the in situ produced N. crassa cellulolytic system (1.0 FPU/g SB) with commercial cellulase and ß-glucosidase mixture at low activity (6.0 FPU/g SB) increased ethanol production to 27.6 g/l or 84.7 % of theoretical yield (based on SB cellulose and hemicellulose sugar content). The combined dilute-acid pretreatment and bioconversion led to maximum cellulose and hemicellulose hydrolysis 73.3 % and 89.6 %, respectively.

Hydrothermal processing and enzymatic hydrolysis of sorghum bagasse for fermentable carbohydrates production.

Untreated and hydrothermally treated sorghum bagasse (SB) was hydrolyzed to simple sugars by the synergistic action of cellulases and hemicellulases produced by the fungi Fusarium oxysporum and Neurospora crassa. Synergism between the two lignocellulolytic systems was maximized with the application of higher fraction of N. crassa enzymes. Hydrothermolysis of SB was studied at a wide range of treatment times and temperatures. At intense pretreatment conditions (210 degrees C for 20 min; logR(0)=4.54), the residual hemicellulose percentage was 17.45%, while formation of inhibitory products, 5-hydromethyl-furfural (HMF), furfural, acetic and formic acid, (0.21, 0.51, 3.36 and 1.80 g/l, respectively) remained in acceptable levels. Maximum conversion of cellulose and total polysaccharides of the untreated SB were 23.18% and 18.79%, respectively. Combining hydrothermal treatment and enzymatic hydrolysis of released oligosaccharides and insoluble solids resulted in improvement of cellulose (approximately 15% increase) and total polysaccharides (two fold) hydrolysis compared to that of untreated SB.