Daly et al. 2021 From lignocellulose to plastics: Knowledge transfer on the degradation approaches by fungi

Daly-et-al-2021-featured-image

Daly P, Cai F, Kubicek CP, Jiang S, Grujic M, Rahimi MJ, Sheteiwy MS, Giles R, Riaz A, de Vries RP, Bayram Akcapinar G, Wei L, Druzhinina IS (2021) From lignocellulose to plastics: Knowledge transfer on the degradation approaches by fungi, Biotechnology Advances, 50,
107770, https://doi.org/10.1016/j.biotechadv.2021.107770.

In this review, we argue that there is much to be learned by transferring knowledge from research on lignocellulose degradation to that on plastic. Plastic waste accumulates in the environment to hazardous levels, because it is inherently recalcitrant to biological degradation. Plants evolved lignocellulose to be resistant to degradation, but with time, fungi became capable of utilising it for their nutrition. Examples of how fungal strategies to degrade lignocellulose could be insightful for plastic degradation include how fungi overcome the hydrophobicity of lignin (e.g. production of hydrophobins) and crystallinity of cellulose (e.g. oxidative approaches). In parallel, knowledge of the methods for understanding lignocellulose degradation could be insightful such as advanced microscopy, genomic and post-genomic approaches (e.g. gene expression analysis). The known limitations of biological lignocellulose degradation, such as the necessity for physiochemical pretreatments for biofuel production, can be predictive of potential restrictions of biological plastic degradation. Taking lessons from lignocellulose degradation for plastic degradation is also important for biosafety as engineered plastic-degrading fungi could also have increased plant biomass degrading capabilities. Even though plastics are significantly different from lignocellulose because they lack hydrolysable C-C or C-O bonds and therefore have higher recalcitrance, there are apparent similarities, e.g. both types of compounds are mixtures of hydrophobic polymers with amorphous and crystalline regions, and both require hydrolases and oxidoreductases for their degradation. Thus, many lessons could be learned from fungal lignocellulose degradation.

Zhao et al. 2021 At least three families of hyphosphere small secreted cysteine-rich proteins can optimize surface properties to a moderately hydrophilic state suitable for fungal attachment

Zhao et al., 2021 Hyphosphere concept

Zhao, Z., Cai, F., Gao, R., Ding, M., Jiang, S., Chen, P., Pang, G., Chenthamara, K., Shen, Q., Bayram Akcapinar, G. and Druzhinina, I.S. (2021), At least three families of hyphosphere small secreted cysteine-rich proteins can optimize surface properties to a moderately hydrophilic state suitable for fungal attachment. Environ Microbiol. https://doi.org/10.1111/1462-2920.15413

The secretomes of filamentous fungi contain a diversity of small secreted cysteine-rich proteins (SSCPs) that have a variety of properties ranging from toxicity to surface activity. Some SSCPs are recognized by other organisms as indicators of fungal presence, but their function in fungi is not fully understood. We detected a new family of fungal surface-active SSCPs (saSSCPs), here named hyphosphere proteins (HFSs). An evolutionary analysis of the HFSs in Pezizomycotina revealed a unique pattern of eight single cysteine residues (C-CXXXC-C-C-C-C-C) and a long evolutionary history of multiple gene duplications and ancient interfungal lateral gene transfers, suggesting their functional significance for fungi with different lifestyles. Interestingly, recombinantly produced saSSCPs from three families (HFSs, hydrophobins and cerato-platanins) showed convergent surface-modulating activity on glass and on poly(ethylene-terephthalate), transforming their surfaces to a moderately hydrophilic state, which significantly favoured subsequent hyphal attachment. The addition of purified saSSCPs to the tomato rhizosphere had mixed effects on hyphal attachment to roots, while all tested saSSCPs had an adverse effect on plant growth in vitro. We propose that the exceptionally high diversity of saSSCPs in Trichoderma and other fungi evolved to efficiently condition various surfaces in the hyphosphere to a fungal-beneficial state.