ABSTRACT
Research background: An innovative integrated bioprocess system for bioethanol production from raw sugar beet cossettes (SBC) and arabitol from remaining exhausted sugar beet cossettes (ESBC) was studied. This integrated three-stage bioprocess system is an example of the biorefinery concept to maximise the use of raw SBC for the production of high value-added products such as sugar alcohols and bioethanol. Experimental approach: The first stage of the integrated bioprocess system was simultaneous sugar extraction from SBC and its alcoholic fermentation to produce bioethanol in an integrated bioreactor system (vertical column bioreactor and stirred tank bioreactor) containing a high-density suspension of yeast Saccharomyces cerevisiae (30 g/L). The second stage was the pretreatment of ESBC with dilute sulfuric acid to release fermentable sugars. The resulting liquid hydrolysate of ESBC was used in the third stage as a nutrient medium for arabitol production by non-Saccharomyces yeasts (Spathaspora passalidarum CBS 10155 and Spathaspora arborariae CBS 11463). Results and conclusions: The obtained results show that the efficiency of bioethanol production increased with increasing temperature and prolonged residence time in the integrated bioreactor system. The maximum bioethanol production efficiency (87.22 %) was observed at a time of 60 min and a temperature of 36 °C. Further increase in residence time (above 60 min) did not result in the significant increase of bioethanol production efficiency. Weak acid hydrolysis was used for ESBC pretreatment and the highest sugar yield was reached at 200 °C and residence time of 1 min. The inhibitors of the weak acid pretreatment were produced below bioprocess inhibition threshold. The use of the obtained liqiud phase of ESBC hydrolysate for the production of arabitol in the stirred tank bioreactor under constant aeration clearly showed that S. passalidarum CBS 10155 with 8.48 g/L of arabitol (YP/S=0.603 g/g and bioprocess productivity of 0.176 g/(L.h)) is a better arabitol producer than Spathaspora arborariae CBS 10155. Novelty and scientific contribution: An innovative integrated bioprocess system for the production of bioethanol and arabitol was developed based on the biorefinery concept. This three-stage bioprocess system shows great potential for maximum use of SBC as a feedstock for bioethanol and arabitol production and it could be an example of a sustainable 'zero waste' production system.
ABSTRACT
The underutilized biomass and different organic waste streams are nowadays in the focus of research for renewable energy production due to the effusive use of fossil fuels and greenhouse gas emission. In addition, one of the major environmental problems is also a constant increase of the number of organic waste streams. In a lot of countries, sustainable waste management, including waste prevention and reduction, has become a priority as a means to reduce pollution and greenhouse gas emission. Application of biogas technology is one of the promising methods to provide solutions for both actual energy-related and environmental problems. This review aims to present conventional and novel biogas production systems, as well as purification and upgrading technologies, nowadays applicable on a large scale, with a special focus on the CO2 and H2S removal. It also gives an overview of feedstock and the parameters important for biogas production, together with digestate utilization and application of molecular biology in order to improve the biogas production.
ABSTRACT
Agaricus bisporus, also known as the white button mushroom or champignon, is the most cultivated mushroom species worldwide. In addition to its favorable nutrient profile, it contains a number of compounds with antioxidant, antibacterial, anti-inflammatory, antitumor, and immunomodulatory activities. Waste biomass is a secondary product obtained from A. bisporus during the harvesting stage. It is underused, although it could be a cheap source of polysaccharides and antioxidants for use in food and feed production, or a source of nutraceuticals and cosmeceuticals. In this study, waste biomass was used as raw material for extraction of crude polysaccharides. The mean amount of crude polysaccharides extracted was 106 g/kg dry weight debris-free mushroom waste biomass. The crude polysaccharides recovered contained 11.57% α-glucan and 16.37% ß-glucan. Total carbohydrates composed 44.18%. No significant differences were found in the Fourier transform infrared spectra, which confirmed the presence of protein, α-glucan, and ß-glucan in all samples; phenols were detected only in waste biomass and market-ready A. bisporus fruiting bodies. The total phenol content in methanol extracts of waste biomass and A. bisporus fruiting bodies was 6.16 and 11.25 mg gallic acid equivalents/g extract, respectively. Antioxidant capacities of methanol extracts from waste biomass, as determined by spectrophotometric techniques, were 22.67 µmol Trolox/g extract (ABTS radical scavenging), 51.77 µmol Fe2+/g extract (ferric-reducing antioxidant power), and 51.52% (DPPH radical scavenging). Although these values were lower than those for A. bisporus fruiting bodies, the waste biomass has great potential for use in food, feed, and other bioproducts of economic importance.
Subject(s)
Agaricus/chemistry , Antioxidants/chemistry , Fungal Polysaccharides/chemistry , Solid Waste/analysis , BiomassABSTRACT
Submerged batch and repeated fed-batch cultivation techniques were used for mycelia cultivation and polysaccharide production of the Lingzhi or Reishi medicinal mushroom Ganoderma lucidum. Although most publications use various Asiatic G. lucidum strains, the growth of the strain Ga.l 4 (Biotechnical Faculty Strain Collection, Ljubljana, Slovenia), originally isolated from the Slovenian forest, is much faster. The results between the batch and repeated fed-batch cultivation are compared with the polysaccharide production in batch cultivation. From the aspect of biomass production, the best results were obtained in repeated fed-batch after 44 days, where 12.4 g/L of dry fungal biomass was obtained.
Subject(s)
Biomass , Fungal Polysaccharides/chemistry , Fungal Polysaccharides/metabolism , Ganoderma/metabolism , Bioreactors , Culture Techniques , Time FactorsABSTRACT
Solid state cultivation of Ganoderma lucidum biomass, strain BFWS Gal 4, originally isolated from the Slovenian forest, was studied in a horizontal stirred tank reactor. Periodic mixing of N = 80 rpm, 2 min/day was used. Production of fungal polysaccharides and fungal biomass on solid substrate based on beech sawdust, olive oil, and mineral salts was studied. Optimal moisture of the solid matrix was in the range of 80% to 74%. When the moisture content dropped below 57%, the growth of the mycelium and polysaccharide production stopped, but it revived when wet air was applied in further processing. Final concentration of biomass was 0.68 mg/g of solid substrate, while proportions of extracellular and intracellular polysaccharides were 4.5 mg/g and 1.05 mg/g, respectively.
