The effect of particle size and amount of inoculum on fungal treatment of wheat straw and wood chips

Conversion of Lignocellulosic Biomass Into Valuable Feed for Ruminants Using White Rot Fungi

White rot fungi can degrade lignin and improve the nutritional value of highly lignified biomass for ruminants. We screened for excellent fungi-biomass combinations by investigating the improvement of digestibility of wheat straw, barley straw, oat straw, rapeseed straw, miscanthus, new reed, spent reed from thatched roofs, and cocoa shells after colonisation by Ceriporiopsis subvermispora (CS), Lentinula edodes (LE), and Pleurotus eryngii (PE) (indicated by increased in vitro gas production [IVGP]). First, growth was evaluated for three fungi on all types of biomass, over a period of 17 days in race tubes. CS grew faster than LE and PE on all types of biomass. LE did not grow on cocoa shells, while growth rate of CS and PE on cocoa shells was lower compared to other types of biomass. After this first screening, all types of biomass, excluding the cocoa shells, were colonised by the three fungal strains for 8 weeks. Treatment with CS and LE improved IVGP more than treatment with PE. Methane production was reduced in six combinations of biomass with CS, four with LE, and three with PE. Six types of biomass were selected for treatment with CS and four were selected for treatment with CS and LE, to determine the net improvement of nutritional value (increased IVGP corrected for dry matter loss) after 2, 4, 6, 7 and 8 weeks of treatment. The highest net improvement was found for CS and LE treated rapeseed straw (86% and 20%, respectively) and spent reed (80% and 43%, respectively). All treatments decreased dry matter, lignin and hemicellulose, the latter two both in absolute amount and content. In conclusion, net improvement of highly lignified biomasses by CS was greater than LE, with the nutritional value of rapeseed straw and spent reed being significantly improved by both fungi.

Optimizing fungal treatment of lignocellulosic agro-industrial by-products to enhance their nutritional value

This study delves into the dynamic interaction between various fungal strains, substrates, and treatment durations to optimize the nutritional value of these by-products. Six fungi, including Penicillium chrysogenum, Fusarium sp., Fusarium oxysporum, Fusarium solani, Penicillium crustosum, and Cosmospora viridescens, were evaluated across three substrates: wheat straw (WS), cedar sawdust (CW), and olive pomace (OP) over treatment periods of 4, 8, and 12 weeks. The study discerned profound impacts of these fungi across multiple parameters, including cellulose variation (C.var), lignin variation (L.var), and in vitro true digestibility variation (IVTD.var). Our results demonstrated that the various fungi had a significant effect on all parameters (p < .001). Noteworthy, F. oxysporum and F. solani emerged as exemplars, displaying notable lignin degradation, cellulose liberation, and IVTD enhancement. Importantly, P. crustosum demonstrated substantial cellulose degradation, exhibiting optimal efficacy in just 4 weeks for all substrates. Notably, F. sp. excelled, yielding favorable results when treating WS. P. chrysogenum achieved optimal outcomes with 8-week treatment for WS. Both Fusarium sp. and P. chrysogenum exhibited slight cellulose release, with remarkable reduction of WS lignin compared to other substrates. Especially, WS and OP displayed superior digestibility enhancements relative to CW. It should be noted that the treatment duration further shaped these outcomes, as prolonged treatment (12 weeks) fostered greater benefits in lignin degradation and digestibility, albeit with concomitant cellulose degradation. These findings underscore the intricate balance between fungal strains, substrates, and treatment durations in optimizing the nutritional value of lignocellulosic agro-industrial by-products. The outcomes of this study lead to the enhancement in the overall value of by-products, promoting sustainable livestock feed and advancing agricultural sustainability.

The use of cellulolytic Aspergillus sp. inoculum to improve the quality of Pineapple compost

Pineapple litter has a complex polymer of cellulose, hemicellulose, and lignin, which makes them difficult to decompose. However, pineapple litter has great potential to be a good organic material source for the soil when completely decomposed. The addition of inoculants can facilitate the composting process. This study investigated whether the addition of cellulolytic fungi inoculants to pineapple litters improves the efficiency of the composting processes. The treatments were KP1 = pineapple leaf litter: cow manure (2:1), KP2 = pineapple stem litter: cow manure (2:1), KP3 = pineapple leaf litter: pineapple stem litter: cow manure P1 (leaf litter and 1% inoculum), P2 (stem litter and 1% inoculum), and P3 (leaf + stem litters and 1% inoculum). The result showed that the number of Aspergillus sp. spores on corn media was 5.64 x 10⁷ spores/mL, with viability of 98.58%. Aspergillus sp. inoculum improved the quality of pineapple litter compost, based on the enhanced contents of C, N, P, K, and the C/N ratio, during the seven weeks of composting. Moreover, the best treatment observed in this study was P1. The C/N ratios of compost at P1, P2, and P3 were within the recommended range of organic fertilizer which was 15-25%, with a Carbon/Nitrogen proportion of 11.3%, 11.8%, and 12.4% (P1, P2, and P3), respectively.

Challenges and Opportunities in Scaling up Architectural Applications of Mycelium-Based Materials with Digital Fabrication

In an increasing effort to address the environmental challenges caused by the currently linear economic paradigm of “produce, use, and discard”, the construction industry has been shifting towards a more circular model. A circular economy requires closing of the loops, where the end-of-life of a building is considered more carefully, and waste is used as a resource. In comparison to traditional building materials such as timber, steel and concrete, mycelium-based materials are renewable alternatives that use organic agricultural and industrial waste as a key ingredient for production, and do not rely on mass extraction or exploitation of valuable finite or non-finite resources. Mycelium-based materials have shown their potential as a more circular and economically competitive alternative to conventional synthetic materials in numerous industries ranging from packaging, electronic prototyping, furniture, fashion to architecture. However, application of mycelium-based materials in the construction industry has been limited to small-scale prototypes and architectural installations due to low mechanical properties, lack of standardisation in production methods and material characterisation. This paper aims to review the current state of the art in research and applications of mycelium-based materials across disciplines, with a particular focus on digital methods of fabrication, production, and design. The information gathered from this review will be synthesised to identify key challenges in scaling up applications of mycelium-based materials as load-bearing structural elements in architecture and suggest opportunities and directions for future research.

Aerial warfare: An inducible production of volatile bioactive metabolites in a novel species of Scytinostroma sp

Antimicrobial volatile organic compounds (VOCs) may provide fungi an advantage over other competing microorganisms. As these defensive metabolites are often produced in response to microbial competitors, they are easily overlooked in axenic cultures. We used media supplemented with spent medium from Candida albicans to induce the expression of a broad-spectrum antimicrobial response in a previously uncharacterised white-rot fungus, Scytinostroma sp. Crude extractions of Scytinostroma sp. metabolites were found to be cytotoxic to fibroblast cells and antimicrobial to filamentous fungi, yeasts and Gram-positive bacteria. Volatile antimicrobial activity was observed for Scytinostroma sp. cultures and metabolite extracts using antimicrobial assays in bi-compartmentalised plates. Culture headspace analysis using solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS) revealed a pronounced shift in Scytinostroma sp. VOCs when cultured on media supplemented with C. albicans spent medium. We observed a significant increase in the levels of 45 identified VOCs, including 7 metabolites with reported antimicrobial activity. Using preparative HPLC combined with GC-MS, we determined that isovelleral is likely to be the main broad-spectrum antimicrobial metabolite produced by Scytinostroma sp. Isovelleral is a sesquiterpene dialdehyde with both antibiotic and antifeedant properties, previously detected in fruit bodies of other Basidiomycetes.

Mechanistic insight in the selective delignification of wheat straw by three white-rot fungal species through quantitative 13C-IS py-GC-MS and whole cell wall HSQC NMR

BACKGROUND

The white-rot fungi Ceriporiopsis subvermispora (Cs), Pleurotus eryngii (Pe), and Lentinula edodes (Le) have been shown to be high-potential species for selective delignification of plant biomass. This delignification improves polysaccharide degradability, which currently limits the efficient lignocellulose conversion into biochemicals, biofuels, and animal feed. Since selectivity and time efficiency of fungal delignification still need optimization, detailed understanding of the underlying mechanisms at molecular level is required. The recently developed methodologies for lignin quantification and characterization now allow for the in-depth mapping of fungal modification and degradation of lignin and, thereby, enable resolving underlying mechanisms.

RESULTS

Wheat straw treated by two strains of Cs (Cs1 and Cs12), Pe (Pe3 and Pe6) and Le (Le8 and Le10) was characterized using semi-quantitative py-GC-MS during fungal growth (1, 3, and 7 weeks). The remaining lignin after 7 weeks was quantified and characterized using 13C lignin internal standard based py-GC-MS and whole cell wall HSQC NMR. Strains of the same species showed similar patterns of lignin removal and degradation. Cs and Le outperformed Pe in terms of extent and selectivity of delignification (Cs ≥ Le >> Pe). The highest lignin removal [66% (w/w); Cs1] was obtained after 7 weeks, without extensive carbohydrate degradation (factor 3 increased carbohydrate-to-lignin ratio). Furthermore, though after treatment with Cs and Le comparable amounts of lignin remained, the structure of the residual lignin vastly differed. For example, Cα-oxidized substructures accumulated in Cs treated lignin up to 24% of the total aromatic lignin, a factor two higher than in Le-treated lignin. Contrarily, ferulic acid substructures were preferentially targeted by Le (and Pe). Interestingly, Pe-spent lignin was specifically depleted of tricin (40% reduction). The overall subunit composition (H:G:S) was not affected by fungal treatment.

CONCLUSIONS

Cs and Le are both able to effectively and selectively delignify wheat straw, though the underlying mechanisms are fundamentally different. We are the first to identify that Cs degrades the major β-O-4 ether linkage in grass lignin mainly via Cβ-O-aryl cleavage, while Cα-Cβ cleavage of inter-unit linkages predominated for Le. Our research provides a new insight on how fungi degrade lignin, which contributes to further optimizing the biological upgrading of lignocellulose.

Potential use of cowpea (Vigna unguiculata (L.) Walp.) stover treated with white-rot fungi as rabbit feed

BACKGROUND

Lignin inhibitory effects within the cell wall structure constitute a serious drawback in maximizing the utilization of fibrous feedstuffs in animal feeding. Therefore treatments that promote efficient delignification of these materials must be applied. This study evaluated the potential of white-rot fungi to upgrade the nutritive value of cowpea stover for rabbit feeding.

RESULTS

There was an increase in the crude protein content of all substrates as a result of fungi treatments, reaching a net gain of 13% for Pleurotus citrinopileatus incubation. Overall, net losses of dry and organic matter occurred during fungi treatments. Although the fiber content remained identical, higher consumption of cell wall contents was measured for P. citrinopileatus incubation (between 40 and 45%). The incubation period did not influence lignin degradation for any of the fungi treatments. Differences within the fungal degradation mechanisms indicate that P. citrinopileatus treatment was most effective, enhancing in vitro organic matter digestibility by around 30% compared with the control.

CONCLUSION

Treatment of cowpea stover with P. citrinopileatus led to an efficient delignification process which resulted in higher in vitro organic matter digestibility, showing its potential in the nutritional valorization of this feedstuff. © 2017 Society of Chemical Industry.

Differences between two strains of Ceriporiopsis subvermispora on improving the nutritive value of wheat straw for ruminants

AIM

This study evaluated differences between two strains of Ceriporiopsis subvermispora on improving the nutritive value and in vitro degradability of wheat straw.

METHODS AND RESULTS

Wheat straw was treated with the fungi for 7 weeks. Weekly samples were analysed for ergosterol content, in vitro gas production (IVGP), chemical composition and lignin-degrading enzyme activity. Ergosterol data showed CS1 to have a faster initial growth than CS2 and reaching a stationary phase after 3 weeks. The IVGP of CS1-treated wheat straw exceeded the control earlier than CS2 (4 vs 5 weeks). CS1 showed a significantly higher (P < 0·001) selectivity in lignin degradation compared to CS2. Both strains showed peak activity of laccase and manganese peroxidase (MnP) at week 1. CS1 showed a significantly higher (P < 0·001) laccase activity, but lower (P = 0·008) MnP activity compared to CS2.

CONCLUSION

Both CS strains improved the nutritive value of wheat straw. Variation between strains was clearly demonstrated by their growth pattern and enzyme activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

The differences among the two strains provide an opportunity for future selection and breeding programs in improving the extent and selectivity of lignin degradation in agricultural biomass.