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Solomon, Kevin V.

Publications and source records attributed to Solomon, Kevin V..

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Biological Upcycling of Plastics Waste

Plastic wastes accumulate in the environment, impacting wildlife and human health and representing a significant pool of inexpensive waste carbon that could form feedstock for the sustainable production of commodity chemicals, monomers, and specialty chemicals. Current mechanical recycling technologies are not economically attractive due to the lower-quality plastics that are produced in each iteration. Thus, the development of a plastics economy requires a solution that can deconstruct plastics and generate value from the deconstruction products. Biological systems can provide such value by allowing for the processing of mixed plastics waste streams via enzymatic specificity and using engineered metabolic pathways to produce upcycling targets. We focus on the use of biological systems for waste plastics deconstruction and upcycling. We highlight documented and predicted mechanisms through which plastics are biologically deconstructed and assimilated and provide examples of upcycled products from biological systems. Additionally, we detail current challenges in the field, including the discovery and development of microorganisms and enzymes for deconstructing non–polyethylene terephthalate plastics, the selection of appropriate target molecules to incentivize development of a plastic bioeconomy, and the selection of microbial chassis for the valorization of deconstruction products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Characterization and rank assignment criteria for the anaerobic fungi (Neocallimastigomycota)

Establishing a solid taxonomic framework is crucial for enabling discovery and documentation efforts. This ensures effective communication between scientists as well as reproducibility of results between laboratories, and facilitates the exchange and preservation of biological material. Such framework can only be achieved by establishing clear criteria for taxa characterization and rank assignment. Within the anaerobic fungi (phylum Neocallimastigomycota), the need for such criteria is especially vital. Difficulties associated with their isolation, maintenance and long-term storage often result in limited availability and loss of previously described taxa. To this end, we provide here a list of morphological, microscopic, phylogenetic and phenotypic criteria for assessment and documentation when characterizing newly obtained Neocallimastigomycota isolates. We also recommend a polyphasic rank-assignment scheme for novel genus-, species- and strain-level designations for newly obtained Neocallimastigomycota isolates.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Hydrolysis of lignocellulose by anaerobic fungi produces free sugars and organic acids for two–stage fine chemical production with Kluyveromyces marxianus

Development of the bioeconomy is driven by our ability to access the energy-rich carbon trapped in recalcitrant plant materials. Current strategies to release this carbon rely on expensive enzyme cocktails and physicochemical pretreatment, producing inhibitory compounds that hinder subsequent microbial bioproduction. Anaerobic fungi are an appealing solution as they hydrolyze crude, untreated biomass at ambient conditions into sugars that can be converted into value-added products by partner organisms. However, some carbon is lost to anaerobic fungal fermentation products. To improve efficiency and recapture this lost carbon, we built a two-stage bioprocessing system pairing the anaerobic fungus Piromyces indianae with the yeast Kluyveromyces marxianus, which grows on a wide range of sugars and fermentation products. In doing so we produce fine and commodity chemicals directly from untreated lignocellulose. P. indianae efficiently hydrolyzed substrates such as corn stover and poplar to generate sugars, fermentation acids, and ethanol, which K. marxianus consumed while producing 2.4 g/L ethyl acetate. An engineered strain of K. marxianus was also able to produce 550 mg/L 2-phenylethanol and 150 mg/L isoamyl alcohol from P. indianae hydrolyzed lignocellulosic biomass. Despite the use of crude untreated plant material, production yields were comparable to optimized rich yeast media due to the use of all available carbon including organic acids, which formed up to 97% of free carbon in the fungal hydrolysate. Furthermore, this work demonstrates that anaerobic fungal pretreatment of lignocellulose can sustain the production of fine chemicals at high efficiency by partnering organisms with broad substrate versatility.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Anaerobic gut fungi are an untapped reservoir of natural products

Anaerobic fungi (class Neocallimastigomycetes) thrive as low-abundance members of the herbivore digestive tract. The genomes of anaerobic gut fungi are poorly characterized and have not been extensively mined for the biosynthetic enzymes of natural products such as antibiotics. Here, we investigate the potential of anaerobic gut fungi to synthesize natural products that could regulate membership within the gut microbiome. Here, complementary 'omics' approaches were combined to catalog the natural products of anaerobic gut fungi from four different representative species: Anaeromyces robustus (A. robustus), Caecomyces churrovis (C. churrovis), Neocallimastix californiae (N. californiae), and Piromyces finnis (P. finnis). In total, 146 genes were identified that encode biosynthetic enzymes for diverse types of natural products, including nonribosomal peptide synthetases and polyketide synthases.

59 BASIC BIOLOGICAL SCIENCES↗