It should be based on weight of solid substrate(Media contents).

Is it inorganic nitrogen or organic nitrogen or mixture, in what ratio? It can also be part of study.

Absolutely agree on Ghanshyam's opinion. You should calculate the weight of solid media contents.

Good luck

I agree, also you can read:

Aldo Amaro-Reyes, Jorge Gracida, Nelson Huizache-Peña, Norberto Elizondo-García, José Salazar-Martínez, Blanca E. García Almendárez, Carlos Regalado, On-site hydrolytic enzymes production from fungal co-cultivation of Bermuda grass and corn cob, Bioresource Technology, Available online 19 April 2016, ISSN 0960-8524, http://dx.doi.org/10.1016/j.biortech.2016.04.070.

(http://www.sciencedirect.com/science/article/pii/S0960852416305570)

I also agree with Ghanshyam's opinion. However, for enzyme production in SSF it's very important to consider the C:N ratio and the source of N (organic or inorganic) because this will depends on the strain.

Good luck!

Dear Nizzal, in addition to the excellent comments from our colleagues, the total N and C content should be determined. These could greatly vary if you use natural substrates (i.e. rice, meals) or controlled if you use synthetic media. I think you should answer Ghanshyam's question about  the source of N  (organic or inorganic) that could be included as part of the investigation. Good luck!

Yes, 1% nitrogen source is determine based on weight of the solid substrate you use for the production of enzyme. For 5 gm of substrates it will be 0.05 gm nitrogen source.

All the best.

I agree with all colegues, I like Rual consideration. I want to add just take into consideration your 5 g as dry basis

You may calculate it on dry weight basis of the solid bed. So you need to determine moisture content of the solid bed. This will take care of season dependant variations of the solid bed weight. .

 1% nitrogen source is determine based on weight of the solid substrate you use for the production of enzyme. For 5 gm of substrates it will be 0.05 gm nitrogen source you should add to the 100 ml of media.

1% nitrogen source is determined on the solid substrate you use. But i think that you should take into consideration the moisture content if the solid bed and the evaporation that may take place or study them as dependent variations

I agree with all answers above .