Irradiation of Yarrowia lipolytica NRRL YB-567 creating novel strains with enhanced ammonia and oil production on protein and carbohydrate substrates

What makes Yarrowia lipolytica well suited for industry?

Yarrowia lipolytica possesses natural and engineered traits that make it a good host for the industrial bioproduction of chemicals, fuels, foods, and pharmaceuticals. In recent years, academic and industrial researchers have assessed its potential, developed synthetic biology techniques, improved its features, scaled its processes, and identified its limitations. Both publications and patents related to Y. lipolytica have shown a drastic increase during the past decade. Here, we discuss the characteristics of this yeast that make it suitable for industry and the remaining challenges for its wider use at large scale. We present evidence herein that shows the importance and potential of Y. lipolytica in bioproduction such that it may soon be one of the preferred choices of industry.

[Capacity of the oleaginous yeast Clavispora lusitaniae Hi2 to transform agroindustrial residues into lipids]

BACKGROUND

Single-cell oils obtained from oleaginous microorganisms by using lignocellulosic waste hydrolysates are an alternative for producing biodiesel.

AIMS

To isolate a yeast strain able to produce lipids from centrifuged nejayote (CN), hydrolyzed nejayote solids (HNS) and hydrolyzed sugarcane bagasse (HSB).

METHODS

In order to identify the yeasts recovered, 26S ribosomal DNA was sequenced. The metabolic profile was assessed by using API20C AUX strips. The nutritional characterization of CN, HNS and HSB was performed by quantifying reducing sugars, total carbohydrates, starch, protein and total nitrogen. The biomass and lipid production ability were evaluated by performing growth kinetics of Clavispora lusitaniae Hi2 in combined culture media.

RESULTS

Six oleaginous yeast strains were isolated and identified, selecting C. lusitaniae Hi2 to study its lipids production by using nejayote. The C. lusitaniae Hi2 strain can use glucose, xylose, arabinose, galactose and cellobiose as carbon sources. Cultures of C. lusitaniae Hi2 presented the best biomass (5.6±0.28 g/L) and lipid production (0.99±0.09 g/L) at 20 h of incubation with the CN:HNS media in the 25:75 and 50:50 ratios, respectively.

CONCLUSIONS

The use of CN, HNS and HSB for the growth of C. lusitaniae Hi2 is an option to take advantage of these agro-industrial residues and generate compounds of biotechnological interest.

Intelligent host engineering for metabolic flux optimisation in biotechnology

Optimising the function of a protein of length N amino acids by directed evolution involves navigating a 'search space' of possible sequences of some 20N. Optimising the expression levels of P proteins that materially affect host performance, each of which might also take 20 (logarithmically spaced) values, implies a similar search space of 20P. In this combinatorial sense, then, the problems of directed protein evolution and of host engineering are broadly equivalent. In practice, however, they have different means for avoiding the inevitable difficulties of implementation. The spare capacity exhibited in metabolic networks implies that host engineering may admit substantial increases in flux to targets of interest. Thus, we rehearse the relevant issues for those wishing to understand and exploit those modern genome-wide host engineering tools and thinking that have been designed and developed to optimise fluxes towards desirable products in biotechnological processes, with a focus on microbial systems. The aim throughput is 'making such biology predictable'. Strategies have been aimed at both transcription and translation, especially for regulatory processes that can affect multiple targets. However, because there is a limit on how much protein a cell can produce, increasing kcat in selected targets may be a better strategy than increasing protein expression levels for optimal host engineering.

Sustainable Animal Feed Protein through the Cultivation of YARROWIA Lipolytica on Agro-Industrial Wastes and by-Products

Proteins are essential constituents of animal feeds, which comprise mainly vegetable protein (e.g., soybean meal), which is produced and transported globally. The decoupling of protein-production and livestock-growth areas results in protein deficiencies in certain parts of the world, and in significant environmental stress. Alternative, more sustainable protein feeds are necessary to meet the increasing needs, and to decrease the environmental footprint of animal products. Yeast Single Cell Proteins (SCP), produced locally using various agro-industrial by-product streams, have significant potential as alternative animal feed protein. Particularly, Yarrowia lipolytica, an oleaginous, non-pathogenic microorganism has been characterized as a “workhorse” in biotechnological studies, drawing the attention of many researchers. The present review summarizes available resources on critical issues concerning the applicability and commercialization of Yarrowia lipolytica as an environment-friendly protein source for animal feed. It discusses the sustainability of the yeast SCP production process, it presents the recent advances concerning Yarrowia lipolytica cultivation on low-cost agro-industrial by-products, and it stresses the effects on the health and welfare of productive animals due to the inclusion of Yarrowia lipolytica in their diet. The data presented in this study should facilitate relative research advancement and the commercialization of Yarrowia lipolytica’s use as an alternative protein source/supplement for animal feeds.

Mutants of Yarrowia lipolytica NCIM 3589 grown on waste cooking oil as a biofactory for biodiesel production

Background

Oleaginous yeasts are fast emerging as a possible feedstock for biodiesel production. Yarrowia lipolytica, a model oleaginous yeast is known to utilize a variety of hydrophobic substrates for lipid accumulation including waste cooking oil (WCO). Approaches to increase lipid content in this yeast include metabolic engineering which requires manipulation of multiple genes in the lipid biosynthesis pathway. A classical and cost-effective approach, namely, random chemical mutagenesis on the yeast can lead to increased production of biodiesel as is explored here.

Results

In this study, chemical mutagenesis using the alkylating agent, N- methyl-N′-nitro-N-nitrosoguanidine (MNNG) as well as an additional treatment with cerulenin, a fatty acid synthase inhibitor generated 800 mutants of Y. lipolytica NCIM 3589 (761 MNNG treated and 39 MNNG + cerulenin treated). A three-stage screening using Sudan Black B plate technique, Nile red fluorimetry and total lipid extraction using solvent was performed, which enabled selection of ten high lipid yielding mutants. Time course studies of all the ten mutants were further undertaken in terms of biomass, lipid yield and lipid content to select three stable mutants (YlB6, YlC7 and YlE1) capable of growing and accumulating lipid on WCO, with lipid contents of 55, 60 and 67% as compared to 45% for the wild type. The mutants demonstrated increased volumetric lipid productivities (0.062, 0.044 and 0.041 g L⁻¹ h⁻¹) as compared to the wild type (0.033 g L⁻¹ h⁻¹). The fatty acid profile of the three mutants consisted of a high content of C16 and C18 saturated and monounsaturated fatty acids and was found to be suitable for biodiesel production. The fuel properties, namely, density, kinematic viscosity, total acid number, iodine value of the three mutants were evaluated and found to lie within the limits specified by internationally accepted standards. Additionally, it was noted that the mutants demonstrated better cetane numbers and higher heating values than the wild type strain.

Conclusion

The chemical mutagenesis strategy adopted in this study resulted in the successful isolation of three stable high SCO yielding mutants. The mutants, namely, YlB6, YlC7 and YlE1 exhibited a 1.22, 1.33 and 1.49-fold increase in lipid contents when grown on 100 g L⁻¹ waste cooking oil than the parental yeast strain. The fatty acid methyl ester (FAME) profiles of all the three mutants was determined to be suitable for biodiesel suggesting their potential applicability while simultaneously addressing the management of waste cooking oil.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0790-x) contains supplementary material, which is available to authorized users.

Microbial lipid production by oleaginous yeasts on Laminaria residue hydrolysates

Laminaria residues, major wastes from the kelp industry, can be effectively converted by oleaginous yeasts into microbial lipids as potential feedstock for biodiesel production.