diff --git a/pkg/obiformats/embl_read.go b/pkg/obiformats/embl_read.go
index 876866f..992660c 100644
--- a/pkg/obiformats/embl_read.go
+++ b/pkg/obiformats/embl_read.go
@@ -159,7 +159,7 @@ func EmblChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.BioS
 }
 
 func _ParseEmblFile(
-	input ChannelSeqFileChunk,
+	input ChannelFileChunk,
 	out obiiter.IBioSequence,
 	withFeatureTable bool,
 ) {
@@ -189,7 +189,7 @@ func ReadEMBL(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, er
 
 	buff := make([]byte, 1024*1024*128) // 128 MB
 
-	entry_channel := ReadSeqFileChunk(
+	entry_channel := ReadFileChunk(
 		opt.Source(),
 		reader,
 		buff,
diff --git a/pkg/obiformats/fastaseq_read.go b/pkg/obiformats/fastaseq_read.go
index cb162db..86b5de7 100644
--- a/pkg/obiformats/fastaseq_read.go
+++ b/pkg/obiformats/fastaseq_read.go
@@ -205,7 +205,7 @@ func FastaChunkParser() func(string, io.Reader) (obiseq.BioSequenceSlice, error)
 }
 
 func _ParseFastaFile(
-	input ChannelSeqFileChunk,
+	input ChannelFileChunk,
 	out obiiter.IBioSequence,
 ) {
 
@@ -213,6 +213,7 @@ func _ParseFastaFile(
 
 	for chunks := range input {
 		sequences, err := parser(chunks.Source, chunks.Raw)
+		// log.Warnf("Chunck(%d:%d) -%d- ", chunks.Order, l, sequences.Len())
 
 		if err != nil {
 			log.Fatalf("File %s : Cannot parse the fasta file : %v", chunks.Source, err)
@@ -234,7 +235,7 @@ func ReadFasta(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, e
 
 	buff := make([]byte, 1024*1024)
 
-	chkchan := ReadSeqFileChunk(
+	chkchan := ReadFileChunk(
 		opt.Source(),
 		reader,
 		buff,
diff --git a/pkg/obiformats/fastqseq_read.go b/pkg/obiformats/fastqseq_read.go
index fe11869..43a5aca 100644
--- a/pkg/obiformats/fastqseq_read.go
+++ b/pkg/obiformats/fastqseq_read.go
@@ -296,7 +296,7 @@ func FastqChunkParser(quality_shift byte) func(string, io.Reader) (obiseq.BioSeq
 }
 
 func _ParseFastqFile(
-	input ChannelSeqFileChunk,
+	input ChannelFileChunk,
 	out obiiter.IBioSequence,
 	quality_shift byte,
 ) {
@@ -326,7 +326,7 @@ func ReadFastq(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, e
 
 	buff := make([]byte, 1024*1024)
 
-	chkchan := ReadSeqFileChunk(
+	chkchan := ReadFileChunk(
 		opt.Source(),
 		reader,
 		buff,
diff --git a/pkg/obiformats/fastseq_write_fasta.go b/pkg/obiformats/fastseq_write_fasta.go
index 4c9f7ef..7aa71fb 100644
--- a/pkg/obiformats/fastseq_write_fasta.go
+++ b/pkg/obiformats/fastseq_write_fasta.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"os"
 	"strings"
+	"time"
 
 	log "github.com/sirupsen/logrus"
 
@@ -132,7 +133,7 @@ func WriteFasta(iterator obiiter.IBioSequence,
 
 	nwriters := opt.ParallelWorkers()
 
-	chunkchan := WriteSeqFileChunk(file, opt.CloseFile())
+	chunkchan := WriteFileChunk(file, opt.CloseFile())
 
 	header_format := opt.FormatFastSeqHeader()
 
@@ -140,6 +141,9 @@ func WriteFasta(iterator obiiter.IBioSequence,
 
 	go func() {
 		newIter.WaitAndClose()
+		for len(chunkchan) > 0 {
+			time.Sleep(time.Millisecond)
+		}
 		close(chunkchan)
 		log.Debugf("Writing fasta file done")
 	}()
@@ -151,7 +155,7 @@ func WriteFasta(iterator obiiter.IBioSequence,
 
 			log.Debugf("Formating fasta chunk %d", batch.Order())
 
-			chunkchan <- SeqFileChunk{
+			chunkchan <- FileChunk{
 				Source: batch.Source(),
 				Raw:    FormatFastaBatch(batch, header_format, opt.SkipEmptySequence()),
 				Order:  batch.Order(),
@@ -166,7 +170,7 @@ func WriteFasta(iterator obiiter.IBioSequence,
 
 	log.Debugln("Start of the fasta file writing")
 	go ff(iterator)
-	for i := 0; i < nwriters-1; i++ {
+	for i := 1; i < nwriters; i++ {
 		go ff(iterator.Split())
 	}
 
diff --git a/pkg/obiformats/fastseq_write_fastq.go b/pkg/obiformats/fastseq_write_fastq.go
index e3959c1..08e47f6 100644
--- a/pkg/obiformats/fastseq_write_fastq.go
+++ b/pkg/obiformats/fastseq_write_fastq.go
@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"io"
 	"os"
-	"sync"
 	"time"
 
 	log "github.com/sirupsen/logrus"
@@ -87,11 +86,6 @@ func FormatFastqBatch(batch obiiter.BioSequenceBatch,
 	return &bs
 }
 
-type FileChunk struct {
-	text  []byte
-	order int
-}
-
 func WriteFastq(iterator obiiter.IBioSequence,
 	file io.WriteCloser,
 	options ...WithOption) (obiiter.IBioSequence, error) {
@@ -104,27 +98,25 @@ func WriteFastq(iterator obiiter.IBioSequence,
 
 	nwriters := opt.ParallelWorkers()
 
-	chunkchan := WriteSeqFileChunk(file, opt.CloseFile())
+	chunkchan := WriteFileChunk(file, opt.CloseFile())
 
 	header_format := opt.FormatFastSeqHeader()
 
 	newIter.Add(nwriters)
 
-	var waitWriter sync.WaitGroup
-
 	go func() {
 		newIter.WaitAndClose()
 		for len(chunkchan) > 0 {
 			time.Sleep(time.Millisecond)
 		}
 		close(chunkchan)
-		waitWriter.Wait()
+		log.Debugf("Writing fastq file done")
 	}()
 
 	ff := func(iterator obiiter.IBioSequence) {
 		for iterator.Next() {
 			batch := iterator.Get()
-			chunk := SeqFileChunk{
+			chunk := FileChunk{
 				Source: batch.Source(),
 				Raw:    FormatFastqBatch(batch, header_format, opt.SkipEmptySequence()),
 				Order:  batch.Order(),
@@ -137,7 +129,7 @@ func WriteFastq(iterator obiiter.IBioSequence,
 
 	log.Debugln("Start of the fastq file writing")
 	go ff(iterator)
-	for i := 0; i < nwriters-1; i++ {
+	for i := 1; i < nwriters; i++ {
 		go ff(iterator.Split())
 	}
 
diff --git a/pkg/obiformats/seqfile_chunk_read.go b/pkg/obiformats/file_chunk_read.go
similarity index 88%
rename from pkg/obiformats/seqfile_chunk_read.go
rename to pkg/obiformats/file_chunk_read.go
index b729829..17eb0c1 100644
--- a/pkg/obiformats/seqfile_chunk_read.go
+++ b/pkg/obiformats/file_chunk_read.go
@@ -11,13 +11,13 @@ import (
 
 type SeqFileChunkParser func(string, io.Reader) (obiseq.BioSequenceSlice, error)
 
-type SeqFileChunk struct {
+type FileChunk struct {
 	Source string
 	Raw    *bytes.Buffer
 	Order  int
 }
 
-type ChannelSeqFileChunk chan SeqFileChunk
+type ChannelFileChunk chan FileChunk
 
 type LastSeqRecord func([]byte) int
 
@@ -34,15 +34,15 @@ type LastSeqRecord func([]byte) int
 //
 // Returns:
 // None
-func ReadSeqFileChunk(
+func ReadFileChunk(
 	source string,
 	reader io.Reader,
 	buff []byte,
-	splitter LastSeqRecord) ChannelSeqFileChunk {
+	splitter LastSeqRecord) ChannelFileChunk {
 	var err error
 	var fullbuff []byte
 
-	chunk_channel := make(ChannelSeqFileChunk)
+	chunk_channel := make(ChannelFileChunk)
 
 	fileChunkSize := len(buff)
 
@@ -95,8 +95,10 @@ func ReadSeqFileChunk(
 				}
 
 				if len(buff) > 0 {
-					io := bytes.NewBuffer(slices.Clone(buff))
-					chunk_channel <- SeqFileChunk{source, io, i}
+					cbuff := slices.Clone(buff)
+					io := bytes.NewBuffer(cbuff)
+					// log.Warnf("chuck %d :Read %d bytes from file %s", i, io.Len(), source)
+					chunk_channel <- FileChunk{source, io, i}
 					i++
 				}
 
@@ -120,7 +122,7 @@ func ReadSeqFileChunk(
 		// Send the last chunk to the channel
 		if len(buff) > 0 {
 			io := bytes.NewBuffer(slices.Clone(buff))
-			chunk_channel <- SeqFileChunk{source, io, i}
+			chunk_channel <- FileChunk{source, io, i}
 		}
 
 		// Close the readers channel when the end of the file is reached
diff --git a/pkg/obiformats/seqfile_chunk_write.go b/pkg/obiformats/file_chunk_write.go
similarity index 88%
rename from pkg/obiformats/seqfile_chunk_write.go
rename to pkg/obiformats/file_chunk_write.go
index 573ea20..820a821 100644
--- a/pkg/obiformats/seqfile_chunk_write.go
+++ b/pkg/obiformats/file_chunk_write.go
@@ -8,16 +8,16 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-func WriteSeqFileChunk(
+func WriteFileChunk(
 	writer io.WriteCloser,
-	toBeClosed bool) ChannelSeqFileChunk {
+	toBeClosed bool) ChannelFileChunk {
 
 	obiiter.RegisterAPipe()
-	chunk_channel := make(ChannelSeqFileChunk)
+	chunk_channel := make(ChannelFileChunk)
 
 	go func() {
 		nextToPrint := 0
-		toBePrinted := make(map[int]SeqFileChunk)
+		toBePrinted := make(map[int]FileChunk)
 		for chunk := range chunk_channel {
 			if chunk.Order == nextToPrint {
 				log.Debugf("Writing chunk: %d of length %d bytes",
diff --git a/pkg/obiformats/genbank_read.go b/pkg/obiformats/genbank_read.go
index f9dfed2..b0a0dfc 100644
--- a/pkg/obiformats/genbank_read.go
+++ b/pkg/obiformats/genbank_read.go
@@ -198,7 +198,7 @@ func GenbankChunkParser(withFeatureTable bool) func(string, io.Reader) (obiseq.B
 	}
 }
 
-func _ParseGenbankFile(input ChannelSeqFileChunk,
+func _ParseGenbankFile(input ChannelFileChunk,
 	out obiiter.IBioSequence,
 	withFeatureTable bool) {
 
@@ -225,7 +225,7 @@ func ReadGenbank(reader io.Reader, options ...WithOption) (obiiter.IBioSequence,
 
 	buff := make([]byte, 1024*1024*128) // 128 MB
 
-	entry_channel := ReadSeqFileChunk(
+	entry_channel := ReadFileChunk(
 		opt.Source(),
 		reader,
 		buff,
diff --git a/pkg/obiformats/json_writer.go b/pkg/obiformats/json_writer.go
index b51210c..2e5cf76 100644
--- a/pkg/obiformats/json_writer.go
+++ b/pkg/obiformats/json_writer.go
@@ -7,7 +7,6 @@ import (
 	"os"
 	"strconv"
 	"strings"
-	"sync"
 	"time"
 
 	"github.com/goccy/go-json"
@@ -58,9 +57,17 @@ func JSONRecord(sequence *obiseq.BioSequence) []byte {
 	return text
 }
 
-func FormatJSONBatch(batch obiiter.BioSequenceBatch) []byte {
+func FormatJSONBatch(batch obiiter.BioSequenceBatch) *bytes.Buffer {
 	buff := new(bytes.Buffer)
+
 	json := bufio.NewWriter(buff)
+
+	if batch.Order() == 0 {
+		json.WriteString("[\n")
+	} else {
+		json.WriteString(",\n")
+	}
+
 	n := batch.Slice().Len() - 1
 	for i, s := range batch.Slice() {
 		json.WriteString("  ")
@@ -71,8 +78,7 @@ func FormatJSONBatch(batch obiiter.BioSequenceBatch) []byte {
 	}
 
 	json.Flush()
-
-	return buff.Bytes()
+	return buff
 }
 
 func WriteJSON(iterator obiiter.IBioSequence,
@@ -84,14 +90,10 @@ func WriteJSON(iterator obiiter.IBioSequence,
 	file, _ = obiutils.CompressStream(file, opt.CompressedFile(), opt.CloseFile())
 
 	newIter := obiiter.MakeIBioSequence()
-
 	nwriters := opt.ParallelWorkers()
 
-	obiiter.RegisterAPipe()
-	chunkchan := make(chan FileChunk)
-
+	chunkchan := WriteFileChunk(file, opt.CloseFile())
 	newIter.Add(nwriters)
-	var waitWriter sync.WaitGroup
 
 	go func() {
 		newIter.WaitAndClose()
@@ -99,7 +101,6 @@ func WriteJSON(iterator obiiter.IBioSequence,
 			time.Sleep(time.Millisecond)
 		}
 		close(chunkchan)
-		waitWriter.Wait()
 	}()
 
 	ff := func(iterator obiiter.IBioSequence) {
@@ -107,62 +108,31 @@ func WriteJSON(iterator obiiter.IBioSequence,
 
 			batch := iterator.Get()
 
-			chunkchan <- FileChunk{
-				FormatJSONBatch(batch),
-				batch.Order(),
+			ss := FileChunk{
+				Source: batch.Source(),
+				Raw:    FormatJSONBatch(batch),
+				Order:  batch.Order(),
 			}
+
+			chunkchan <- ss
 			newIter.Push(batch)
 		}
 		newIter.Done()
 	}
 
-	next_to_send := 0
-	received := make(map[int]FileChunk, 100)
-
-	waitWriter.Add(1)
-	go func() {
-		for chunk := range chunkchan {
-			if chunk.order == next_to_send {
-				if next_to_send > 0 {
-					file.Write([]byte(",\n"))
-				}
-				file.Write(chunk.text)
-				next_to_send++
-				chunk, ok := received[next_to_send]
-				for ok {
-					file.Write(chunk.text)
-					delete(received, next_to_send)
-					next_to_send++
-					chunk, ok = received[next_to_send]
-				}
-			} else {
-				received[chunk.order] = chunk
-			}
-
-		}
-
-		file.Write([]byte("\n]\n"))
-		file.Close()
-
-		log.Debugln("End of the JSON file writing")
-		obiiter.UnregisterPipe()
-		waitWriter.Done()
-
-	}()
-
 	log.Debugln("Start of the JSON file writing")
-	file.Write([]byte("[\n"))
-	go ff(iterator)
-	for i := 0; i < nwriters-1; i++ {
+	for i := 1; i < nwriters; i++ {
 		go ff(iterator.Split())
 	}
+	go ff(iterator)
 
 	return newIter, nil
 }
 
 func WriteJSONToStdout(iterator obiiter.IBioSequence,
 	options ...WithOption) (obiiter.IBioSequence, error) {
-	options = append(options, OptionDontCloseFile())
+	options = append(options, OptionCloseFile())
+
 	return WriteJSON(iterator, os.Stdout, options...)
 }
 
diff --git a/pkg/obioptions/version.go b/pkg/obioptions/version.go
index 53233c0..a786cbe 100644
--- a/pkg/obioptions/version.go
+++ b/pkg/obioptions/version.go
@@ -7,7 +7,7 @@ import (
 // TODO: The version number is extracted from git. This induces that the version
 // corresponds to the last commit, and not the one when the file will be
 // commited
-var _Commit = "3d06978"
+var _Commit = "69ef175"
 var _Version = "Release 4.2.0"
 
 // Version returns the version of the obitools package.
diff --git a/pkg/obiseq/attributes.go b/pkg/obiseq/attributes.go
index 5a604d9..26fff9c 100644
--- a/pkg/obiseq/attributes.go
+++ b/pkg/obiseq/attributes.go
@@ -16,11 +16,12 @@ import (
 //
 // Returns:
 //   - A set of strings containing the keys of the BioSequence attributes.
-func (s *BioSequence) AttributeKeys(skip_container bool) obiutils.Set[string] {
+func (s *BioSequence) AttributeKeys(skip_container, skip_definition bool) obiutils.Set[string] {
 	keys := obiutils.MakeSet[string]()
 
 	for k, v := range s.Annotations() {
-		if !skip_container || !obiutils.IsAContainer(v) {
+		if !((skip_container && obiutils.IsAContainer(v)) ||
+			(skip_definition && k == "definition")) {
 			keys.Add(k)
 		}
 	}
@@ -38,8 +39,8 @@ func (s *BioSequence) AttributeKeys(skip_container bool) obiutils.Set[string] {
 //
 // Returns:
 //   - A set of strings containing the keys of the BioSequence.
-func (s *BioSequence) Keys(skip_container bool) obiutils.Set[string] {
-	keys := s.AttributeKeys(skip_container)
+func (s *BioSequence) Keys(skip_container, skip_definition bool) obiutils.Set[string] {
+	keys := s.AttributeKeys(skip_container, skip_definition)
 	keys.Add("id")
 
 	if s.HasSequence() {
diff --git a/pkg/obiseq/biosequenceslice.go b/pkg/obiseq/biosequenceslice.go
index 24993ec..12210a6 100644
--- a/pkg/obiseq/biosequenceslice.go
+++ b/pkg/obiseq/biosequenceslice.go
@@ -150,11 +150,11 @@ func (s BioSequenceSlice) Size() int {
 	return size
 }
 
-func (s BioSequenceSlice) AttributeKeys(skip_map bool) obiutils.Set[string] {
+func (s BioSequenceSlice) AttributeKeys(skip_map, skip_definition bool) obiutils.Set[string] {
 	keys := obiutils.MakeSet[string]()
 
 	for _, k := range s {
-		keys = keys.Union(k.AttributeKeys(skip_map))
+		keys = keys.Union(k.AttributeKeys(skip_map, skip_definition))
 	}
 
 	return keys
diff --git a/pkg/obitax/default_taxonomy.go b/pkg/obitax/default_taxonomy.go
index d963f0f..9a10ac1 100644
--- a/pkg/obitax/default_taxonomy.go
+++ b/pkg/obitax/default_taxonomy.go
@@ -1,16 +1,17 @@
 package obitax
 
-import "log"
+import log "github.com/sirupsen/logrus"
 
 var __defaut_taxonomy__ *Taxonomy
 
 func (taxonomy *Taxonomy) SetAsDefault() {
+	log.Infof("Set as default taxonomy %s", taxonomy.Name())
 	__defaut_taxonomy__ = taxonomy
 }
 
 func (taxonomy *Taxonomy) OrDefault(panicOnNil bool) *Taxonomy {
 	if taxonomy == nil {
-		return __defaut_taxonomy__
+		taxonomy = __defaut_taxonomy__
 	}
 
 	if panicOnNil && taxonomy == nil {
diff --git a/pkg/obitools/obicsv/options.go b/pkg/obitools/obicsv/options.go
index 08f320d..cff5e4c 100644
--- a/pkg/obitools/obicsv/options.go
+++ b/pkg/obitools/obicsv/options.go
@@ -1,6 +1,7 @@
 package obicsv
 
 import (
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obioptions"
 	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitools/obiconvert"
 	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiutils"
 	"github.com/DavidGamba/go-getoptions"
@@ -66,6 +67,7 @@ func CSVOptionSet(options *getoptions.GetOpt) {
 func OptionSet(options *getoptions.GetOpt) {
 	obiconvert.InputOptionSet(options)
 	obiconvert.OutputModeOptionSet(options)
+	obioptions.LoadTaxonomyOptionSet(options, false, false)
 	CSVOptionSet(options)
 }
 
diff --git a/pkg/obitools/obicsv/sequence.go b/pkg/obitools/obicsv/sequence.go
index 71e80e2..cc3023b 100644
--- a/pkg/obitools/obicsv/sequence.go
+++ b/pkg/obitools/obicsv/sequence.go
@@ -121,7 +121,7 @@ func NewCSVSequenceIterator(iter obiiter.IBioSequence, options ...WithOption) *I
 			if len(batch.Slice()) == 0 {
 				log.Panicf("first batch should not be empty")
 			}
-			auto_slot := batch.Slice().AttributeKeys(true).Members()
+			auto_slot := batch.Slice().AttributeKeys(true, true).Members()
 			slices.Sort(auto_slot)
 			CSVKeys(auto_slot)(opt)
 			iter.PushBack()
diff --git a/pkg/obitools/obicsv/writer.go b/pkg/obitools/obicsv/writer.go
index c11342c..941f99a 100644
--- a/pkg/obitools/obicsv/writer.go
+++ b/pkg/obitools/obicsv/writer.go
@@ -55,7 +55,7 @@ func WriteCSV(iterator *ICSVRecord,
 
 	nwriters := opt.ParallelWorkers()
 
-	chunkchan := obiformats.WriteSeqFileChunk(file, opt.CloseFile())
+	chunkchan := obiformats.WriteFileChunk(file, opt.CloseFile())
 
 	newIter.Add(nwriters)
 
@@ -72,7 +72,7 @@ func WriteCSV(iterator *ICSVRecord,
 
 			log.Debugf("Formating CSV chunk %d", batch.Order())
 
-			ss := obiformats.SeqFileChunk{
+			ss := obiformats.FileChunk{
 				Source: batch.Source(),
 				Raw: FormatCVSBatch(
 					batch,