Co-production Of Value-added Products Research Articles

Biomass waste valorization assisted by microwaves: a feasible approach for the co-production of value-added products

Biomass waste valorization assisted by microwaves: a feasible approach for the co-production of value-added products

Strategies to Produce Cost-Effective Third-Generation Biofuel From Microalgae

Third-generation biofuel produced from microalgae is a viable solution to global energy insecurity and climate change. Despite an annual current global algal biomass production of 38 million litres, commercialization confronts significant economic challenges. However, cost minimization strategies, particularly for microalgae cultivation, have largely been excluded from recent studies. Therefore, this review provides essential insights into the technologies and economics of cost minimization strategies for large-scale applications. Cultivation of microalgae through aquafarming, in wastewater, or for biogas upgrading, and co-production of value-added products (VAPs) such as photo-bioreactors, protein, astaxanthin, and exopolysaccharides can drastically reduce biodiesel production costs. For instance, the co-production of photo-bioreactors and astaxanthin can reduce the cost of biodiesel production from $3.90 to $0.54 per litre. Though many technical challenges need to be addressed, the economic analysis reveals that incorporating such cost-effective strategies can make the biorefinery concept feasible and profitable. The cost of producing microalgal biodiesel can be lowered to $0.73kg−1dry weight when cultivated in wastewater or $0.54L−1when co-produced with VAPs. Most importantly, access to co-product markets with higher VAPs needs to be encouraged as the global market for microalgae-based VAPs is estimated to rise to $53.43 billion in 2026. Therefore, policies that incentivize research and development, as well as the production and consumption of microalgae-based biodiesel, are important to reduce the large gap in production cost that persists between biodiesel and petroleum diesel.

Metabolic engineering of Bacillus subtilis for the co-production of uridine and acetoin.

In this study, a uridine and acetoin co-production pathway was designed and engineered in Bacillus subtilis for the first time. A positive correlation between acetoin and uridine production was observed and investigated. By disrupting acetoin reductase/2,3-butanediol dehydrogenasegenebdhA, the acetoin and uridine yield was increased while 2,3-butanediol formation was markedly reduced. Subsequent overexpression of the alsSD operon further improved acetoin yield and abolished acetate formation. After optimization of fermentation medium, key supplementation strategies of yeast extract and soybean meal hydrolysate were identified and applied to improve the co-production of uridine and acetoin. With a consumption of 290.33g/L glycerol, the recombinant strain can accumulate 40.62g/L uridine and 60.48g/L acetoin during 48h of fed-batch fermentation. The results indicate that simultaneous production of uridine and acetoin is an efficient strategy for balancing the carbon metabolism in engineered Bacillus subtilis. More importantly, co-production of value-added products is a possible way to improve the economics of uridine fermentation.

Industrial Wastewater Treatment Using Phycoremediation Technologies and Co-Production of Value-Added Products

Algae are a diverse group of photosynthetic organisms with profound bioremediation potential and industrial applications that can reduce the cost of expenditure on energy and fuels. Algae have been applied to various applications from fuels and medicines to wastewater treatment. Potential applications of phycoremediation have instigated laboratories to reinforce the development of algal-based technologies for better exploitation of their bioremediation potential and by-product generation ability. Many species of algae have been studied and utilized for their function in wastewater treatment. Certain technological drawbacks need to be addressed to manage the shortcomings of algae for industrial usage. This review mainly focuses on the state of the art applications of phycotechnology for wastewater remediation. Many problems related to algal technology have also been exemplified and discussed such as contamination, decreasing the resilience time and increasing the biomass of the algal culture. Possible solutions of these bottlenecks have been suggested to better apply phycotechnology for wastewater remediation in industries considering the environmental issues. Recently, the concept of genetic engineering is found very useful that has increased the potential of phycotechnology reducing the resilience time considerably. On the contrary, the negative impact of the algal-based technologies on the environment and economy has also been deliberated in order to effectively utilize and manage this important organism with utmost benefit. Lastly, the review illuminates the scope and options of future research in the area of phycoremediation technologies.

Co-production of 11\u03b1-hydroxyprogesterone and ethanol using recombinant yeast expressing fungal steroid hydroxylases

BackgroundBioethanol production from sustainable sources of biomass that limit effect on food production are needed and in a biorefinery approach co-products are desirable, obtained from both the plant material and from the microbial biomass. Fungal biotransformation of steroids was among the first industrial biotransformations allowing corticosteroid production. In this work, the potential of yeast to produce intermediates needed in corticosteroid production is demonstrated at laboratory scale following bioethanol production from perennial ryegrass juice.ResultsGenes encoding the 11α-steroid hydroxylase enzymes from Aspergillus ochraceus (11α-SHAoch) and Rhizopus oryzae (CYP509C12) transformed into Saccharomyces cerevisiae for heterologous constitutive expression in p425TEF. Both recombinant yeasts (AH22:p11α-SHAoch and AH22:p509C12) exhibited efficient progesterone bioconversion (on glucose minimal medial containing 300 µM progesterone) producing either 11α-hydroxyprogesterone as the sole metabolite (AH22:p11α-SHAoch) or a 7:1 mixture of 11α-hydroxyprogesterone and 6β-hydroxyprogesterone (AH22:p509C12). Ethanol yields for AH22:p11α-SHAoch and AH22:p509C12 were comparable resulting in ≥75% conversion of glucose to alcohol. Co-production of bioethanol together with efficient production of the 11-OH intermediate for corticosteroid manufacture was then demonstrated using perennial ryegrass juice. Integration of the 11α-SHAoch gene into the yeast genome (AH22:11α-SHAoch+K) resulted in a 36% reduction in yield of 11α-hydroxyprogesterone to 174 µmol/L using 300 µM progesterone. However, increasing progesterone concentration to 955 µM and optimizing growth conditions increased 11α-hydroxyprogesterone production to 592 µmol/L product formed.ConclusionsThe progesterone 11α-steroid hydroxylases from A. ochraceus and R. oryzae, both monooxygenase enzymes of the cytochrome P450 superfamily, have been functionally expressed in S. cerevisiae. It appears that these activities in fungi are not associated with a conserved family of cytochromes P450. The activity of the A. ochraceous enzyme was important as the specificity of the biotransformation yielded just the 11-OH product needed for corticosteroid production. The data presented demonstrate how recombinant yeast could find application in rural biorefinery processes where co-production of value-added products (11α-hydroxyprogesterone and ethanol) from novel feedstocks is an emergent and attractive possibility.

Miscanthus as cellulosic biomass for bioethanol production.

The members of the genus Miscanthus are potential feedstocks for biofuels because of the promising high yields of biomass per unit of planted area. This review addresses species, cultivation, and lignocellulose composition of Miscanthus, as well as pretreatment and enzyme saccharification of Miscanthus biomass for ethanol fermentation. The average cellulose contents in dried biomass of Miscanthus floridulus, Miscanthus sinensis, Miscanthus sacchariflorus, and Miscanthus × giganteus (M × G) are 37.2, 37.6, 38.9, and 41.1% wt/wt, respectively. A number of pretreatment methods have been applied in order to enhance digestibility of Miscanthus biomass for enzymatic saccharification. Pretreatment of Miscanthus using liquid hot water or alkaline results in a significant release of glucose; while glucose yields can be 90% or higher if a pretreatment like AFEX that combines both chemical and physical processes is used. As ethanol is produced by yeast fermentation of the hydrolysate from enzymatic hydrolysis of residual solids (pulp) after pretreatment, theoretical ethanol yields are 0.211-0.233 g/g-raw biomass if only cellulose is taken into account. Simultaneous saccharification and fermentation of pretreated M × G and M. lutarioriparius results in experimental ethanol yields of 0.13 and 0.15 g/g-raw biomass, respectively. Co-production of value-added products can reduce the overall production cost of bioethanol.

Simultaneous production of butanol and acetoin by metabolically engineered Clostridium acetobutylicum

Biobutanol is a potential fuel substitute and has been receiving increased attention in recent years. However, the economics of biobutanol production have been hampered by a number of bottlenecks such as high cost of raw material and low yield of solvent. Co-production of value-added products is a possible way to improve the economics of biobutanol production. Here, we present metabolic engineering strategies to substitute the major by-product acetone for a value-added product acetoin during butanol fermentation. By overexpressing the α-acetolactate decarboxylase gene alsD in Clostridium acetobutylicum B3, the acetoin yield was markedly increased while acetone formation was reduced. Subsequent disruption of adc gene effectively abolished acetone formation and further increased acetoin yield. After optimization of fermentation conditions, the alsD-overexpressing adc mutant generated butanol (13.8g/L), acetoin (4.3g/L), and ethanol (3.9g/L), but no acetone. Thus, acetone was completely substituted for acetoin, and both mass yield and product value were improved. This study provides valuable insights into the regulation of acetoin synthesis and should be highly useful for the development of acetoin-derived products like 2,3-butanediol and 2-butanol in C. acetobutylicum.