Beta-glucan production by Botryosphaeria rhodina in different bench-top bioreactors

Jasmonic acid biosynthesis by fungi: derivatives, first evidence on biochemical pathways and culture conditions for production

Jasmonic acid (JA) and its derivatives called jasmonates (JAs) are lipid-derived signalling molecules that are produced by plants and certain fungi. Beside this function, JAs have a great variety of applications in flavours and fragrances production. In addition, they may have a high potential in agriculture. JAs protect plants against infections. Although there is much information on the biosynthesis and function of JA concerning plants, knowledge on these aspects is still scarce for fungi. Taking into account the practical importance of JAs, the objective of this review is to summarize knowledge on the occurrence of JAs from fungal culture media, their biosynthetic pathways and the culture conditions for optimal JA production as an alternative source for the production of these valuable metabolites.

Utilization of sugarcane straw for production of β-glucan biopolymer by Lasiodiplodia theobromae CCT 3966 in batch fermentation process

β-Glucans as emerging biopolymer are widely produced by microorganisms in fermentation processes using commercial sugars which make process non-economic. Lignocellulosic substances are inexpensive carbon sources, which could be exploited for sustainable production of β-glucans. In this study, a lignocellulosic material, namely sugarcane straw (SCS) was utilized for the production of extracellular β-glucan by Lasiodiplodia theobromae CCT3966. SCS was subjected to acid and subsequent alkaline pretreatment, followed by enzymatic saccharification using cellulase enzyme. Quantity of 48.65 g/L glucose was released after enzymatic hydrolysis. β-Glucan production was performed by cultivation of fungal strain in SCS hydrolysate at 28 °C and initial culture pH 7. Highest β-glucan yield and productivity of 0.047 gg^-1 and 0.014 gL^-1h^-1, respectively was obtained at 72 h fermentation time. Kinetic study of β-glucan production revealed experimental biosynthesis of β-glucan from SCS hydrolysate followed the trend generated by Logistic and Luedeking-Piret models. Chemical structure of biopolymer produced showed β-glucan constitution.

Lipid production and characterization by Mortierella (Umbelopsis) isabellina cultivated on lignocellulosic sugars

AIMS

To study and characterize the lipids produced by Mortierella (Umbelopsis) isabellina, during its growth on mixtures of glucose and xylose.

METHODS AND RESULTS

Glucose and xylose were utilized as carbon sources, solely or in blends, under nitrogen-limited conditions, in batch-flask trials (initial sugars at 80 g l^-1 ). Significant lipid production (maximum lipid 17·8 g l^-1 ; lipid in DCW 61·0% w/w; lipid on glucose consumed 0·23 g g^-1 ) occurred on glucose employed solely, while xylose concentration in the growth medium was conversely correlated with lipid accumulation. With increasing xylose concentrations into the blend, lipid storage decreased while xylitol in significant concentrations (up to 24 g l^-1 ) was produced. Irrespective of the sugar blend employed, significant quantities of endopolysaccharides were detected in the first growth steps (in the presence of nitrogen into the medium or barely after its disappearance) while lipids were stored thereafter. Neutral lipids, mainly composed of triacylglycerols, were the main microbial lipid fraction. Phospholipids were quantified both through fractionation and subsequent gravimetric determination and also through determination of phosphorus, and it seemed that the second method was more accurate. Phospholipids were mainly composed of phosphatidylcholine and another nonidentified compound presumably being phosphatidyldimethylethanolamine.

CONCLUSIONS

Mortierella isabellina is suitable to convert lignocellulosic sugars into lipids.

SIGNIFICANCE AND IMPACT OF THE STUDY

Differentiations between metabolism on xylose and glucose were reported. Moreover, this is one of the first reports indicating extensive analysis of microbial lipids produced by M. isabellina.

Medicinal importance of fungal beta-(1-->3), (1-->6)-glucans

Non-cellulosic beta-glucans are now recognized as potent immunological activators, and some are used clinically in China and Japan. These beta-glucans consist of a backbone of glucose residues linked by beta-(1-->3)-glycosidic bonds, often with attached side-chain glucose residues joined by beta-(1-->6) linkages. The frequency of branching varies. The literature suggests beta-glucans are effective in treating diseases like cancer, a range of microbial infections, hypercholesterolaemia, and diabetes. Their mechanisms of action involve them being recognized as non-self molecules, so the immune system is stimulated by their presence. Several receptors have been identified, which include: dectin-1, located on macrophages, which mediates beta-glucan activation of phagocytosis and production of cytokines, a response co-ordinated by the toll-like receptor-2. Activated complement receptors on natural killer cells, neutrophils, and lymphocytes, may also be associated with tumour cytotoxicity. Two other receptors, scavenger and lactosylceramide, bind beta-glucans and mediate a series of signal pathways leading to immunological activation. Structurally different beta-glucans appear to have different affinities toward these receptors and thus generate markedly different host responses. However, the published data are not always easy to interpret as many of the earlier studies used crude beta-glucan preparations with, for the most part, unknown chemical structures. Careful choice of beta-glucan products is essential if their benefits are to be optimized, and a better understanding of how beta-glucans bind to receptors should enable more efficient use of their biological activities.

Production of ?-glucan and related glucan-hydrolases by Botryosphaeria rhodina

AIMS

Characterization of beta-glucan production from Botryosphaeria rhodina DABAC-P82 by detecting simultaneously glucan-hydrolytic enzymes and their localization, culture medium rheology and oxygen transfer.

METHODS AND RESULTS

Mycelium growth, beta-glucan production, substrate consumption and glucan-hydrolytic enzymes were monitored both in shaken flasks and in a 3-l stirred-tank bioreactor. Glucan production (19.7 and 15.2 g l(-1), in flask and bioreactor, respectively) was accompanied by extra-cellular and cell-bound beta-glucanase and beta-glucosidase activities. In the bioreactor scale, in the time interval of 0-78 h the apparent viscosity of the culture broth exhibited a general increase; thereafter, it began to reduce, probably because of the above glucan-hydrolytic activities. Moreover, the culture media collected after 45 h behaved as solid-like materials at shear rates smaller than 0.001 s(-1), as pseudo-plastic liquids in the middle shear rate range and as Newtonian ones at shear rates greater than 1000 s(-1).

CONCLUSION

The greatest beta-glucan accumulation in the bioreactor was found to be associated with nitrogen and dissolved oxygen concentrations smaller than 0.15 g l(-1) and 25%, respectively, and with the peak points of the glucan-degrading enzymes.

SIGNIFICANCE AND IMPACT OF THE STUDY

A careful analysis of the critical factors (such as, culture broth rheology, oxygen mass transfer and glucan-hydrolytic enzymes) limiting the beta-glucan production by B. rhodina is a prerequisite to maximize beta-glucan yield and production, as well as to define the process flow sheet capable of maximizing biopolymer recovery, solvent re-utilization and glucose consumption.

The current status of natural products from marine fungi and their potential as anti-infective agents

A growing number of marine fungi are the sources of novel and potentially life-saving bioactive secondary metabolites. Here, we have discussed some of these novel antibacterial, antiviral, antiprotozoal compounds isolated from marine-derived fungi and their possible roles in disease eradication. We have also discussed the future commercial exploitation of these compounds for possible drug development using metabolic engineering and post-genomics approaches.