Scale-up of PUF-immobilized fungal chitosanase-lipase preparation production

Continuous production of chitooligosaccharides in a column reactor by the PUF-immobilized whole cell enzymes of Mucor circinelloides IBT-83

BACKGROUND

Chitosan oligosaccharides (COS) have great potential for applications in several fields, including agriculture, food industry or medicine. Nevertheless, the large-scale use of COS requires the development of cost-effective technologies for their production. The main objective of our investigation was to develop an effective method of enzymatic degradation of chitosan in a column reactor using Mucor circinelloides IBT-83 cells, immobilized in a polyurethane foam (PUF). These cells serve as a source of chitosanolytic enzymes.

RESULTS

The study revealed that the process of freeze-drying of immobilized mycelium increases the stability of the associated enzymes during chitosan hydrolysis. The use of stabilized preparations as an active reactor bed enables the production of COS at a constant level for 16 reactor cycles (384 h in total), i.e. 216 h longer compared to non-stabilized mycelium. In the hydrolysate, oligomers ranging in structure from dimer to hexamer as well as D-glucosamine were detected. The potential application of the obtained product in agriculture has been verified. The results of phytotests have demonstrated that the introduction of COS into the soil at a concentration of 0.01 or 0.05% w/w resulted in an increase in the growth of Lepidium sativum stem and root, respectively (extensions by 38 and 44% compared to the control sample).

CONCLUSIONS

The research has verified that the PUF-immobilized M. circinelloides IBT-83 mycelium, which has been stabilized through freeze-drying, is a promising biocatalyst for the environmentally friendly and efficient generation of COS. This biocatalyst has the potential to be used in fertilizers.

Biological depolymerization of lignin using laccase harvested from the autochthonous fungus Schizophyllum commune employing various production methods and its efficacy in augmenting in vitro digestibility in ruminants

A laccase-producing hyper performer, Schizophyllum commune, a white-rot fungus, was evaluated for its ability to selectively degrade lignin of diverse crop residues in vitro. Relative analysis of crop residue treatment using laccase obtained from immobilized cells demonstrated degradation of 30-40% in finger millet straw and sorghum stover, 27-32% in paddy straw, 21% in wheat straw, and 26% in maize straw, while 20% lignin degradation was observed when purified and recombinant laccase was used. Further investigations into in vitro dry matter digestibility studies gave promising results recording digestibility of 54-59% in finger millet straw 33-36% in paddy straw and wheat straw, 16% in maize straw for laccase obtained from cell immobilization method, whereas 14% digestibility was observed when purified and recombinant laccase was used. Sorghum stover recorded digestibility of 13-15% across all straws treated with laccase. The results obtained elucidated the positive influence of laccase treatment on lignin degradation and in vitro dry matter digestibility. The present research gave encouraging figures confirming the production of laccase using the cell immobilization method to be an efficient production method commensurate with purified and recombinant laccase under conditions of submerged cultivation, proclaiming a cost-effective, environmentally safe green technology for effectual lignin depolymerization.

Mucoromycota fungi as powerful cell factories for modern biorefinery

Biorefinery employing fungi can be a strategy for valorizing low-cost rest materials, by-products and wastes into several valuable bioproducts through the fungal fermentation. Mucoromycota fungi are soil fungi with a highly versatile metabolic system that positions them as powerful microbial cell factories for biorefinery applications. Lipids, pigments, chitin/chitosan, polyphosphates, ethanol, organic acids and enzymes are main Mucoromycota products that can be refined from the fermentation process and applied in nutrition, chemical or biofuel industries. In addition, Mucoromycota biomass can be used as it is for specific purposes, such as feed. Mucoromycota fungi can be employed in developing co-production processes, whereby several intra- and extracellular products are simultaneously formed in a single fermentation process, and, thus, economic viability of the process can be improved. This mini review provides a comprehensive overview over the recent advances in the production of valuable metabolites by Mucoromycota fungi and fermentation strategies which could be potentially applied in the industrial biorefinery settings. KEY POINTS: • Biorefineries utilizing Mucoromycota fungi as production cell factories can provide a wide range of bioproducts. • Mucoromycota fungi are able to perform co-production of various metabolites in a single fermentation process. • Versatile metabolism of Mucoromycota allows valorization of a various low-cost substrates such as wastes and rest materials.

Enzymatic Modifications of Chitin, Chitosan, and Chitooligosaccharides

Chitin and its N-deacetylated derivative chitosan are two biological polymers that have found numerous applications in recent years, but their further deployment suffers from limitations in obtaining a defined structure of the polymers using traditional conversion methods. The disadvantages of the currently used industrial methods of chitosan manufacturing and the increasing demand for a broad range of novel chitosan oligosaccharides (COS) with a fully defined architecture increase interest in chitin and chitosan-modifying enzymes. Enzymes such as chitinases, chitosanases, chitin deacetylases, and recently discovered lytic polysaccharide monooxygenases had attracted considerable interest in recent years. These proteins are already useful tools toward the biotechnological transformation of chitin into chitosan and chitooligosaccharides, especially when a controlled non-degradative and well-defined process is required. This review describes traditional and novel enzymatic methods of modification of chitin and its derivatives. Recent advances in chitin processing, discovery of increasing number of new, well-characterized enzymes and development of genetic engineering methods result in rapid expansion of the field. Enzymatic modification of chitin and chitosan may soon become competitive to conventional conversion methods.

Oil accumulation and in situ trans/esterification by lipolytic fungal biomass

The goal of this study was to increase the cost-effectiveness of oil production by an oleaginous and lipolytic strain M. circinelloides IBT-83, by optimizing both lipids accumulation in the mycelium containing intracellular lipases, and a one-step process coupling lipids extraction and enzymatic trans/esterification. In optimal conditions (culture medium composed of corn steep solids, plant oil, glucose and NO₃^-) over 50g_d.w./dm³ of biomass containing over 60% of lipids was produced. The lipids extracted with acetone or petroleum ether contain free fatty acids and triacylglycerols. The supplementation of the second solvent with alcohol results in enzymatic trans/esterification of lipids with the yield of over 80% of esters in 1 h. To our knowledge, this is the first suggestion to convert fungal oils into esters during their extraction using intracellular lipases contained in the same fungus. What is important, it is possible to obtain a second product, lipase preparation, in this process.

Waste fat biodegradation and biomodification by Yarrowia lipolytica and a bacterial consortium composed of Bacillus spp. and Pseudomonas putida

Fats, oils, and greases (FOGs) are a particular environmental threat. Biodegradation of FOGs is a challenge and in this study the biodegradation of waste cooking fats, namely butter and olive oil, was studied using a non-conventional yeast, Yarrowia lipolytica strain LFMB 20, and a bioaugmentation product consisting of Bacillus spp. and Pseudomonas putida CP1 strain. The microorganisms were grown aerobically in shake-flask experiments in an enriched medium supplemented with ca 0.85% w/v of waste fat. Analysis of the remaining substrate showed a removal of ca 90% of the fat by the yeast at the end of the incubation, while the bacteria removed ca 95% of both fats. Growth rate, biomass production and biomass yield per unit of fat consumed were all higher for the yeast compared to the bacterial consortium. The bacterial consortium exhibited autolysis and a significant decrease in its DCW value at the late growth phases of both fat substrate cultures. The main fatty acids (FAs) present in both fats were linoleic (Δ9,12C18:2), oleic (Δ9C18:1), palmitic (C16:0), palmitoleic (Δ9C16:1) and stearic (C18:0) acid. Both the bacterial consortium and Y. lipolytica preferentially removed Δ9C18:1 from the medium, while a negative selectivity against C18:0 was reported. Both inocula produced microbial mass that contained intra-cellular lipid quantities, but the bacterial consortium gave significantly higher lipid in DCW values compared with the yeast (maximum values up to ca 63% w/w for the butter and ca 42% w/w for the olive oil while the respective values for both lipids were 22% ± 2% w/w for Y. lipolytica). In all cases, intra-cellular lipids in DCW values decreased during the late growth phases, while their FA composition differed with those of the substrate fat.

Fungal synthesis of chiral phosphonic synthetic platform - Scope and limitations of the method

Chiral hydroxyphosphonates due to their wide range of biological properties are industrially important chemicals. Chemical synthesis of their optical isomers is expensive, time consuming and not friendly to the environment, so biotransformations are under consideration. Among others, these compounds act as enzymes inhibitors. This makes the bioconversions of phosphonates, especially scaling experiments, hard to perform. Biocatalysis is one of the methods that can be applied in synthesis of optically pure compounds. To increase the efficiency of the process with whole cell biocatalysts, it is essential to ensure optimal reaction conditions that minimize cellular stress and can enhance the metabolic activity of cells. The present investigation focuses on the scaling up of the kinetic resolution of racemic mixture of 2-butyryloxy-2-(ethoxy-P-phenylphosphinyl)acetic acid, applying free and immobilized form of the fungal biocatalysts and two operation systems: shake flask and recirculated fixed-bed batch reactor. Protocols of effective mycelium immobilization on polyurethane foams were set for T. purpurogenus IAFB 2512, F. oxysporum, P. commune. The best results of biotransformation were obtained with the immobilized P. commune in the column recirculated fixed-bed batch reactor. The conversion reaches 56% (maximal for the kinetic process) and the enantiomeric enrichment of the isomers mixture ranges between 82 and 93% (93% for ester of R_P,R conformation). All biocatalysts exhibit S_P-preference toward tested compound, what is essential because of importance of the phosphorus atom chirality for its biological activity.