Publisher Summary This chapter discusses the microbial cleavage of sterol side chains. The recent interest in the microbial conversion of sterols to C19 steroids was caused by the increased demand for steroid drugs and the shortage of diosgenin. As the microbial process has to compete with chemical methods, high conversion efficiencies in the presence of large substrate concentrations have to be obtained. These processes are now used on an industrial scale for the production of 17-ketosteroids. Conventional chemical oxidation of the saturated aliphatic chain results in very low yields. However, in using remote oxidation, the removal of the cholesterol side chain proceeds rather efficiently. For the chemical oxidation of unsaturated sterol side chains, there exist few methods. As alternative to chemical methods, the microbial removal of the aliphatic side chain of phytosterols offers a promising method for use of these sterols and has been studied for some time. Recently, processes for the commercial conversion of sterols to C19-steroids by microorganisms have been developed.

Microbial cleavage of sterol side chains.

Biodegradable plastics can make an important contribution to the struggle against increasing environmental pollution through plastics. However, biodegradability is a material property that is influenced by many factors. This review provides an overview of the main environmental conditions in which biodegradation takes place and then presents the degradability of numerous polymers. Polylactide (PLA), which is already available on an industrial scale, and the polyhydroxyalkanoates polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV), which are among the few plastics that have been proven to degrade in seawater, will be discussed in detail, followed by a summary of the degradability of further petroleum-, cellulose-, starch-, protein- and CO2-based biopolymers and some naturally occurring polymers.

https://www.mdpi.com/1996-1944/13/20/4586/pdf

Review on the Biological Degradation of Polymers in Various Environments.

Organotin polyethers are easily synthesized employing interfacial polymerization systems involving the reaction of hydroxyl-containing Lewis bases and organotin halides. A wide variety of organotin-containing polymeric products have been synthesized including those derived from natural and synthetic polymers such as lignin, xylan, cellulose, dextran, and poly(vinyl alcohol). Others have been synthesized employing known drug diols such as dicumarol, DES, and dienestrol and a wide variety of synthetic diols. Included in these materials are the first water soluble organotin polymers. The organotin polyethers exhibit a wide range of biological activities. Some selectively inhibit a number of unwanted bacteria, including Staph. MRSA, and unwanted yeasts such as Candida albicans. Some also inhibit a variety of viruses including those responsible for herpes infections and smallpox. Others show good inhibition of a wide variety of cancer cell lines including cell lines associated with ovarian, colon, lung, prostrate, pancreatic and breast cancer. The synthesis, structural characterization, and biological characterization of these materials is described in this review.

/pdf/organotin-polyethers-as-biomaterials-e5i73eil7y.pdf

Organotin Polyethers as Biomaterials

Recent studies have described the bacterial community residing in the guts of giant pandas, together with the presence of lignocellulolytic enzymes. However, a more comprehensive understanding of the intestinal microbial composition and its functional capacity in giant pandas remains a major goal. Here, we conducted a comparison of bacterial, fungal and homoacetogenic microbial communities from fecal samples taken from two geriatric and two adult captive giant pandas. 16S rDNA amplicon pyrosequencing revealed that Firmicutes and Proteobacteria are the most abundant microbiota in both geriatric and adult giant pandas. However, members of phylum Actinobacteria found in adult giant pandas were absent in their geriatric counterparts. Similarly, ITS1 amplicon pyrosequencing identified developmental changes in the most abundant fungal classes from Sordariomycetes in adult pandas to Saccharomycetes in geriatric pandas. Geriatric pandas exhibited significantly higher abundance of a potential probiotic fungus (Candida tropicalis) as compared to adult pandas, indicating their importance in the normal digestive physiology of aged pandas. Our study also reported the presence of a lignocellulolytic white-rot fungus, Perenniporia medulla-panis, and the evidence of novel homoacetogens residing in the guts of giant pandas.

/pdf/microbial-diversity-and-evidence-of-novel-homoacetogens-in-e7qyvhhxib.pdf

Microbial diversity and evidence of novel homoacetogens in the gut of both geriatric and adult giant pandas (Ailuropoda melanoleuca)

1 -dehydrogenase; AcmC: Cholest-4-en-3- one Hydroxylase; AD: Androst-4-en-3,17-Dione; ADD: Androsta-1,4- Diene-3,17-Dione; APCI: atmospheric pressure chemical ionization; CoA: Coenzyme A; ESI: Electrospray Ionization; KSTD: 3-Ketosteroid- Δ 1 -Dehydrogenase; LC-APCI-MS: Liquid Chromatography- Atmospheric Pressure Chemical Ionization-Mass Spectrometry; SDR: Short-chain Dehydrogenase/Reductase superfamily; Sli: Sterolibacterium; Sdo: Steroidobacter. Abstract Steroid compounds are produced by eukaryotes where they have a variety of chemical structures and play important physiological roles. Many bacteria are capable of transforming and completely degrading steroids under various growth conditions. The microbial metabolism of steroids has gained considerable interest due to its potential applications in industrial and environmental biotechnology. The oxic degradation pathways of steroids and some of the involved enzymes are well characterized. The key players in these pathways are oxygenases which depend on dioxygen as a co-substrate. On the contrary, much less is known about the mechanisms operating under anoxic conditions. Obviously, anoxic bacterial metabolism of steroids should proceed via oxygenase-independent reactions. So far, a few bacteria that can completely degrade steroids in the absence of oxygen were characterized. Surprisingly, all of them belong to denitrifying bacteria and utilize only nitrate as the alternative electron acceptor. Recent studies of anoxic metabolism of steroids using denitrifying bacteria revealed unique and interesting biochemical reactions and enzymes. Here we discuss the current understanding of the biochemistry and molecular biology of bacterial steroid metabolism under anoxic conditions. The aerobic metabolism of steroids is briefly presented for the sake of comparison. Future investigations on anoxic metabolism of steroids will unravel novel aspects of the regulation and evolution of catabolic pathways as well as unprecedented biocatalysts with useful applications in biotechnology.

Oxic and Anoxic Metabolism of Steroids by Bacteria

Microbial degradation of cholesterol.

The cellulolytic activity of several aerobic soil actinomycetes against insoluble cellulose and soluble cellulose derivatives (CMC-carboxymethylcellulose) was studied From the soil, 8 actinomycete strains were isolated after enrichment growth and purification on the same synthetic medium The actinomycete strains were able to degrade insoluble cellulose, with the production of cellobiose and various oligosaccharide intermediates as degradation products, indicating the random attack of the cellulose chain The actinomycete strains showed also a great activity against soluble cellulose (CMC) The viscosity of CMC solutions decreased rapidly and was followed by an increase in reducing compounds The degree of substitution of CMC solutions had an effect on the degradation by the actinomycetes The degree of polymerization did not affect the rate of hydrolysis, however

Cellulolytic activity of aerobic soil actinomycetes.

The microbial biodegradation of cellophane (U.C.B.--Division Sidac) was studied. Preliminary experiments with pure cultures of seven cellulolytic microorganisms (Aspergillus sp., Penicillium sp., Chaetomium crispatum, Ch. globosum, Sclerotium rolfsii and two actinomycetes) revealed that the substrate as such was very recalcitrant, probably due to the occurrence of insoluble coating agents. Therefore, mixed cultures of the above mentioned cellulolytic microorganisms were used as inoculum. The cellophane showed a slow microbial degradation which starts only after 37 days of incubation. This long lag-phase is due to the unaltered presence of the coating agents. However, when the coating agents are extracted with tetrahydrofuran, the biodegradation starts after 10 days, resulting in a biodegradation rate of 85% after 52 days of incubation and a protein content of 30%. The endproduct (30% protein, 60% soluble sugars, 10% residual substrate) will probably be useful as compost.

E. Lamot

Papers

Microbial degradation of cholesterol.

Cellulolytic activity of aerobic soil actinomycetes.

Microbial biodegradation of cellophase.