Daniel Pleissner

Autotrophic and heterotrophic microalgae and cyanobacteria cultivation for food and feed: life cycle assessment

The lack of protein sources in Europe could be reduced with onsite production of microalgae with autotrophic and heterotrophic systems, owing the confirmation of economic and environmental benefits. This study aimed at the life cycle assessment (LCA) of microalgae and cyanobacteria cultivation (Chlorella vulgaris and Arthrospira platensis) in autotrophic and heterotrophic conditions on a pilot industrial scale (in model conditions of Berlin, Germany) with further biomass processing for food and feed products. The comparison of analysis results with traditional benchmarks (protein concentrates) indicated higher environmental impact of microalgae protein powders. However high-moisture extrusion of heterotrophic cultivated C. vulgaris resulted in more environmentally sustainable product than pork and beef. Further optimization of production with Chlorella pyrenoidosa on hydrolyzed food waste could reduce environmental impact in 4.5 times and create one of the most sustainable sources of proteins.

From lignin to nylon: Cascaded chemical and biochemical conversion using metabolically engineered Pseudomonas putida

Cis,cis-muconic acid (MA) is a chemical that is recognized for its industrial value and is synthetically accessible from aromatic compounds. This feature provides the attractive possibility of producing MA from mixtures of aromatics found in depolymerized lignin, the most underutilized lignocellulosic biopolymer. Based on the metabolic pathway, the catechol (1,2-dihydroxybenzene) node is the central element of this type of production process: (i) all upper catabolic pathways of aromatics converge at catechol as the central intermediate, (ii) catechol itself is frequently generated during lignin pre-processing, and (iii) catechol is directly converted to the target product MA by catechol 1,2-dioxygenase. However, catechol is highly toxic, which poses a challenge for the bio-production of MA. In this study, the soil bacterium Pseudomonas putida KT2440 was upgraded to a fully genome-based host for the production of MA from catechol and upstream aromatics. At the core of the cell factories created was a designed synthetic pathway module, comprising both native catechol 1,2-dioxygenases, catA and catA2, under the control of the Pcat promoter. The pathway module increased catechol tolerance, catechol 1,2-dioxygenase levels, and catechol conversion rates. MA, the formed product, acted as an inducer of the module, triggering continuous expression. Cellular energy level and ATP yield were identified as critical parameters during catechol-based production. The engineered MA-6 strain achieved an MA titer of 64.2u202fgu202fL-1 from catechol in a fed-batch process, which repeatedly regenerated the energy levels via specific feed pauses. The developed process was successfully transferred to the pilot scale to produce kilograms of MA at 97.9% purity. The MA-9 strain, equipped with a phenol hydroxylase, used phenol to produce MA and additionally converted o-cresol, m-cresol, and p-cresol to specific methylated variants of MA. This strain was used to demonstrate the entire value chain. Following hydrothermal depolymerization of softwood lignin to catechol, phenol and cresols, MA-9 accumulated 13u202fgu202fL-1 MA and small amounts of 3-methyl MA, which were hydrogenated to adipic acid and its methylated derivative to polymerize nylon from lignin for the first time.

Material Utilization of Organic Residues

Each year, 1.3 billion tons of food waste is generated globally. This waste traces back to industrial and agricultural producers, bakeries, restaurants, and households. Furthermore, lignocellulosic materials, including grass clippings, leaves, bushes, shrubs, and woods, appear in large amounts. Depending on the region, organic waste is either composted, burned directly, or converted into biogas. All of the options set aside the fact that organic residues are valuable resources containing carbohydrates, lipids, proteins, and phosphorus. Firstly, it is clear that avoidance of organic residues is imperative. However, the residues that accumulate nonetheless should be utilized by material means before energy production is targeted. This review presents different processes for the microbial utilization of organic residues towards compounds that are of great importance for the bioeconomy. The focus thereby is on the challenges coming along with downstream processing when the utilization of organic residues is carried out decentralized. Furthermore, a future process for producing lactic acid from organic residues is sketched.

Utilization of organic residues using heterotrophic microalgae and insects

Various organic residues occur globally in the form of straw, wood, green biomass, food waste, feces, manure etc. Other utilization strategies apart from anaerobic digestion, composting and incineration are needed to make use of the whole potential of organic residues as sources of various value added compounds. This review compares the cultivation of heterotrophic microalgae and insects using organic residues as nutrient sources and illuminates their potential with regard to biomass production, productivity and yield, and utilization strategies of produced biomasses. Furthermore, cultivation processes as well as advantages and disadvantages of utilization processes are identified and discussed. It was shown that both heterotrophic algae and insects are able to reduce a sufficient amount of organic residues by converting it into biomass. The biomass composition of both organisms is similar which allows similar utilization strategies in food and feed, chemicals and materials productions. Even though insect is the more complex organism, biomass production can be carried out using simple equipment without sterilization and hydrolysis of organic residues. Contrarily, heterotrophic microalgae require a pretreatment of organic residues in form of sterilization and in most cases hydrolysis. Interestingly, the volumetric productivity of insect biomass exceeds the productivity of algal biomass. Despite legal restrictions, it is expected that microalgae and insects will find application as alternative food and feed sources in the future.

Is seashell powder suitable for phosphate recovery from fermentation broth

This communication elaborates on the use of seashell powder (SP) for the removal of phosphate from lactic acid-containing fermentation broth. Despite extensive past research regarding the application of SP for phosphate removal from wastewater, no information is available for solutions containing various organic compounds. In order to fill this knowledge gap, tests were performed with pure phosphate solution (PPS) and PPS containing 0.83u202fM of three alcohols, ethanol, propanol or 1,2-propanediol, or 0.83u202fM of three organic acids, acetic, propionic or lactic acid. Furthermore, a real fermentation broth (RFB) obtained from the fermentative production of lactic acid from food waste was tested. Using 4.8u202fg SP, more than 95% of phosphate, present at an initial concentration of 50u202fmgu202fL-1, could be removed from PPS and PPS containing alcohols after 120u202fmin. The presence of organic acids reduced the removal capacity of SP and only 55%-73% of the phosphate initially present was removed. The presence of lactic acid also substantially affected the removal of phosphate from RFB when 132u202fmgu202fL-1 phosphate was initially present: after 120u202fmin, only 28.6u202fmgu202fL-1 of phosphate had been removed. The results indicate the use of SP for phosphate removal from fermentation broth, contributing to multi-component utilization of fermentation broth. However, the effects of respective fermentation products on removal capacity should first be tested.

HOW CAN SUSTAINABLE CHEMISTRY CONTRIBUTE TO A CIRCULAR ECONOMY

The transformation from a linear to a circular economy and from a fossil oil-based to a biobased economy creates challenges that need to be solved. Challenges are associated with the introduction of biobased compounds, such as bioplastics, as new compounds, in existing material cycles and the difficulties to separate such compounds in a circular economy from conventionally used materials. The transformation, however, is necessary due to the expected limitation in fossil resources and associated climate and environmental issues. Sustainable chemistry aims on a simultaneous consideration of resource, production, product and recycling. The focus is not only on sustainable transformation of matter, but also on its origin and fate. Whenever biobased products are to be introduced in existing material cycles, following question might be considered beforehand: 1. Are renewable resources available to carry out production processes in order to meet the demand of certain products?, 2. Is the technology available to carry out recycling and production processes efficiently?, 3. How likely is the separate collection of products after use?, 4. Does the product eco-design allow a recycling of resources?, 5. Are additives as unwanted compounds circulated as well?, 6. Are recycled resources useable in repeatedly carried out production processes? and 7. Does society accept products based on recycled resources? Those questions can be addressed when totally new material cycles are generated. The challenge, however, is finding the beginning of an already existing cycle in a circular economy which allows an introduction of new materials and/or production as well as recycling processes.u200b