@kulandai1, unfortunately there is no way to perform individual DADA2 steps in the QIIME 2 implementation.
It might be possible to do something like this:
- import individual denoised samples as
SampleData[Sequences] - dereplicate them
- merge the resulting individual
FeatureTable[Frequency]andFeatureData[Sequence]artifacts using merge and merge-seqs - remove chimeras using vsearch
- cluster and continue on with the analysis
But this is certainly a non-standard workflow, and it might be helpful to take a look at the clustering otus and the filtering chimeric feature sequences tutorials for inspiration.
Another difficulty might be importing the RDS data into QIIME 2, though this older community tutorial might be helpful here.
I can't say that I am overly optimistic about this working, but if you can't simply start by pulling all of the data into QIIME 2 initially, this might let you move forward! The easiest solution may be to merge the RDS files in R using a machine with more than 76 GB of RAM, though I am not familiar enough with that operation to know how much more you would need.