Uses of miscanthus press juice within a green biorefinery platform

Recent Advances in Miscanthus Macromolecule Conversion: A Brief Overview

Miscanthus is a valuable renewable feedstock and has a significant potential for the manufacture of diverse biotechnology products based on macromolecules such as cellulose, hemicelluloses and lignin. Herein, we overviewed the state-of-the art of research on the conversion of miscanthus polymers into biotechnology products comprising low-molecular compounds and macromolecules: bioethanol, biogas, bacterial cellulose, enzymes (cellulases, laccases), lactic acid, lipids, fumaric acid and polyhydroxyalkanoates. The present review aims to assess the potential of converting miscanthus polymers in order to develop sustainable technologies.

Municipal green waste as substrate for the microbial production of platform chemicals

In Germany alone, more than 5·106 tons of municipal green waste is produced each year. So far, this material is not used in an economically worthwhile way. In this work, grass clippings and tree pruning as examples of municipal green waste were utilized as feedstock for the microbial production of platform chemicals. A pretreatment procedure depending on the moisture and lignin content of the biomass was developed. The suitability of grass press juice and enzymatic hydrolysate of lignocellulosic biomass pretreated with an organosolv process as fermentation medium or medium supplement for the cultivation of Saccharomyces cerevisiae, Lactobacillus delbrueckii subsp. lactis, Ustilago maydis, and Clostridium acetobutylicum was demonstrated. Product concentrations of 9.4 gethanol L-1, 16.9 glactic acid L-1, 20.0 gitaconic acid L-1, and 15.5 gsolvents L-1 were achieved in the different processes. Yields were in the same range as or higher than those of reference processes grown in established standard media. By reducing the waste arising in cities and using municipal green waste as feedstock to produce platform chemicals, this work contributes to the UN sustainability goals and supports the transition toward a circular bioeconomy.

Green Biorefinery systems for the production of climate-smart sustainable products from grasses, legumes and green crop residues

Grasses, legumes and green plant wastes represent a ubiquitous feedstock for developing a bioeconomy in regions across Europe. These feedstocks are often an important source of ruminant feed, although much remains unused or underutilised. In addition to proteins, these materials are rich in fibres, sugars, minerals and other components that could also be used as inputs for bio-based product development. Green Biorefinery processes and initiatives are being developed to better capitalise on the potential of these feedstocks to produce sustainable food, feed, materials and energy in an integrated way. Such systems may support a more sustainable primary production sector, enable the valorisation of green waste streams, and provide new business models for farmers. This review presents the current developments in Green Biorefining, focusing on a broad feedstock and product base to include different models of Green Biorefinery. It demonstrates the potential and wide applicability of Green Biorefinery systems, the range of bio-based product opportunities and highlights the way forward for their broader implementation. While the potential for new products is extensive, quality control approval will be required prior to market entry.

Fermentative α-Humulene Production from Homogenized Grass Clippings as a Growth Medium

Green waste, e.g., grass clippings, is currently insufficiently recycled and has untapped potential as a valuable resource. Our aim was to use juice from grass clippings as a growth medium for microorganisms. Herein, we demonstrate the production of the sesquiterpene α-humulene with the versatile organism Cupriavidus necator pKR-hum on a growth medium from grass clippings. The medium was compared with established media in terms of microbial growth and terpene production. C. necator pKR-hum shows a maximum growth rate of 0.43 h^-1 in the grass medium and 0.50 h^-1 in a lysogeny broth (LB) medium. With the grass medium, 2 mg/L of α-humulene were produced compared to 10 mg/L with the LB medium. By concentrating the grass medium and using a controlled bioreactor in combination with an optimized in situ product removal, comparable product concentrations could likely be achieved. To the best of our knowledge, this is the first time that juice from grass clippings has been used as a growth medium without any further additives for microbial product synthesis. This use of green waste as a material represents a new bioeconomic utilization option of waste materials and could contribute to improving the economics of grass biorefineries.

Investigation of lactic acid production by pressurized liquid hot water from cultivated Miscanthus × giganteus

The production of lactic acid, a polylactic acid monomer from energy crop Miscanthus × giganteus lignocellulosic biomass cultivated in Izmir was investigated. Liquid hot water (LHW) pretreatment was carried out at a temperature range of 140-200 °C, pressure 100 to 200 bar and reaction time of 15-45 min at a fixed flow rate of 2 mL/min using D-optimal experimental plan. The optimum conditions were elicited as 140 °C, 100 bar and 45 minutes, yielding the highest reducing sugar content of 77.32 mg/g, whereas 1.25 mg/mL arabinose and 1.35 mg/mL xylose as monomeric sugars. Subsequently, the enzymatic hydrolysis was applied to the solid fraction. The optimum conditions for enzymatic hydrolysis were determined as 5% (w/v) solid/liquid ratio, 20 FPU/mL enzyme loading and 72 hours, revealing the highest amount of reducing sugar as 200 mg/mL. LHW hydrolysate was used as a production medium for lactic acid manufacturing in submerged fermentation by Rhizopus oryzae. The maximum lactic acid content was found to be 6.8 g/L at 24 hours, whereas the lactic acid yield was 0.28 g/L.h. The sequential design of LHW, followed by enzymatic hydrolysis and submerged lactic acid fermentation can be utilized in industry, contributing to the bioeconomy.

Material utilization of green waste: a review on potential valorization methods

Considering global developments like climate change and the depletion of fossil resources, the use of new and sustainable feedstocks such as lignocellulosic biomass becomes inevitable. Green waste comprises heterogeneous lignocellulosic biomass with low lignin content, which does not stem from agricultural processes or purposeful cultivation and therefore mainly arises in urban areas. So far, the majority of green waste is being composted or serves as feedstock for energy production. Here, the hitherto untapped potential of green waste for material utilization instead of conventional recycling is reviewed. Green waste is a promising starting material for the direct extraction of valuable compounds, the chemical and fermentative conversion into basic chemicals as well as the manufacturing of functional materials like electrodes for electro-biotechnological applications through carbonization. This review serves as a solid foundation for further work on the valorization of green waste.

A review of nondairy kefir products: their characteristics and potential human health benefits

Functional foods are foods that, in addition to having nutrients, contain in their composition ingredients that act specifically on body functions associated with the control and reduction of the risk of developing some diseases. In this sense, kefir, a group of microorganisms in symbiosis, mainly yeasts and lactic acid bacteria, stands out. The trend of ingesting kefir has been focused on the development of products that serve specific consumers, such as those who are lactose-intolerant, vegans and vegetarians, and consumers in general who seek to combine the consumption of functional products with the improvement of their health and lifestyle. This overview provides an insight into kefir, presenting the technological process to produce a nondairy beverage and evidence of the benefits of its use to reduce the risk of disease. We also discuss regulatory aspects of products fermented using kefir. Until now, the use of kefir (isolated microorganism, kefiran, or fermented product) has demonstrated the potential to promote an increase in the number of bifidobacteria in the colon and an increase in the glycemic control while reducing the blood cholesterol and balancing the intestinal microbiota, which helps in reducing constipation and diarrhea, improving intestinal permeability, and stimulating and balancing the immune system. However, the literature still has gaps that need to be clarified, such as the consumption dose of kefir or its products to cause some health benefit.