Enhancing in vitro ruminal digestibility of oil palm empty fruit bunch by biological pre-treatment with Ganoderma lucidum fungal culture

The changes in lignocellulosic biomass composition and in vitro rumen digestibility of oil palm empty fruit bunch (OPEFB) after pre-treatment with the fungus Ganoderma lucidum were evaluated. The results demonstrated that the pre-treatment for 2–12 weeks has gradually degraded the OPEFB in a time-dependent manner; whereby lignin, cellulose, and hemicellulose were respectively degraded by 41.0, 20.5, and 26.7% at the end of the incubation period. The findings were corroborated using the physical examination of the OPEFB by scanning electron microscopy. Moreover, the OPEFB pre-treated for 12 weeks has shown the highest in vitro digestibility of dry (77.20%) and organic (69.78%) matter, where they were enhanced by 104.07 and 96.29%, respectively, as compared to the untreated control. The enhancement in the in vitro ruminal digestibility was negatively correlated with the lignin content in the OPEFB. Therefore, biologically delignified OPEFB with G. lucidum fungal culture pre-treatment have the potential to be utilized as one of the ingredients for the development of a novel ruminant forage.


Reviewer 1 No. Issue/comment/suggestion by the reviewer
Response by the authors 2. The work was not well set for objectives to be investigated.
As stated in the manuscript, the objectives of the study were to evaluate the changes in fibre composition and in vitro rumen digestibility of OPEFB pre-treated with Ganoderma lucidum fungal culture across different incubation period. We believed that all experiments were well set to achieve the objectives, as stated by Reviewer 2. The fibre composition was recorded for every 2 weeks interval for a period of 12 weeks of incubation, and uninoculated OPEFB served as control. Then, the OPEFB pre-treated for different duration was further evaluated for in vitro rumen gas production and digestibility. Treated and untreated samples of OPEFB were also analyzed under SEM to observe physical changes. Therefore, we disagree to the comment by Reviewer 1. 3. Many research works in this area has been reported but the authors have not made sufficient reviews with relevant data.
Many relevant references that related to the use of crop residue, and biological/fungal treatments of crop residues were reviewed and cited. Among of the references are No. 10,12,13,14,15,16,27,33,and 42. 4

. No new innovations have been found and
reported under this experiment.
There was no published article or data found on the use of Ganoderma lucidum to biologically delignify OPEFB, and improve its in vitro ruminal digestibility. Other studies reported the use of different organic materials as the forage, and different fungi species for pretreatment. Therefore, we agreed with Reviewer 2, and disagreed with Reviewer 1. 5. Both the Abstract and Conclusion were not well wrapped up using the significant findings under this experiment.
The abstract was modified to include the key findings of the study. The conclusion was not modified because the authors believed that there is no need to mention the results data in the conclusion section, as this will cause redundancy of information. 6. In particular, comparison of the treated OPEFB after various periods should have been stated comparatively among the treatments.
The changes of fiber composition, and in vitro rumen digestibility of the OPEFB among the treatments (across pre-treatment period) were already stated clearly in the results of the study. Thus, no further change was made. 7. The authors did not show any suggestions or recommendations to further implement the treated OPEFB in the possible feeding interventions.
The limitations, recommendations for future research, and potential applications of the treated OPEFB were stated in the final paragraph of the results and discussion section (L362 -L373).

Reviewer 2 No. Issue/comment/suggestion by the reviewer
Response by the authors 8. The study investigated the enhancing of the nutritive value of oil palm empty fruit bunch after a fungal culture treatment. This is a comprehensive and very interesting study for increasing the nutritive value after reducing the lignocellulose content by fungal degradation.
The study was well-conducted with reasonable replicates.
The authors would like to appreciate the merits given to the study and manuscript.
9. Because Reishi is used in traditional medicine in the East, its price is high. Would it be profitable to use it to improve the nutritional value of fruit and vegetable by-products? that is, is the process very expensive? Well, when a fruit and vegetable by-product is used, it is to replace a more expensive food. And if the treatment of the by-product with Reishi is expensive, then the cost of the ration will not be lowered. have you evaluated these aspects? Could Reishi affect palatability?
The authors understood the concern raised by the reviewer. Firstly, the G. lucidum or Reishi used in traditional medicine is the basidiocarp (fruiting body). However, the present study used mycelium culture which is easier to culture and multiply on carbon rich organic materials. Unfortunately, the cost-effective aspect was not evaluated in present study, but the authors believe that the use of mycelial culture of G. lucidum will not affect on the cost much as they can easily proliferate. The costeffective aspect can be evaluated in a study after the treated OPEFB is mixed with other ingredients to produce a balanced diet for ruminants, as stated in L372. 10. L10-L13-L153-L155-L157 …. Universiti?
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