diff --git a/obitests/obitools/obiconvert/gbpln1088.4Mb.fasta.gz b/obitests/obitools/obiconvert/gbpln1088.4Mb.fasta.gz
new file mode 100644
index 0000000..1db096a
Binary files /dev/null and b/obitests/obitools/obiconvert/gbpln1088.4Mb.fasta.gz differ
diff --git a/obitests/obitools/obiconvert/test.sh b/obitests/obitools/obiconvert/test.sh
index 12db4d0..7fd72c1 100755
--- a/obitests/obitools/obiconvert/test.sh
+++ b/obitests/obitools/obiconvert/test.sh
@@ -13,6 +13,11 @@ CMD=obiconvert
 #
 ######
 TEST_DIR="$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")"
+
+if [ -z "$TEST_DIR" ] ; then
+   TEST_DIR="."
+fi
+
 OBITOOLS_DIR="${TEST_DIR/obitest*/}build"
 export PATH="${OBITOOLS_DIR}:${PATH}"
 
@@ -99,6 +104,36 @@ else
 fi
 
 
+((ntest++))
+if obiconvert -Z "${TEST_DIR}/gbpln1088.4Mb.fasta.gz" \
+                 > "${TMPDIR}/xxx.fasta.gz" && \
+   zdiff "${TEST_DIR}/gbpln1088.4Mb.fasta.gz" \
+                 "${TMPDIR}/xxx.fasta.gz" 
+then
+    log "$MCMD: converting large fasta file to fasta OK" 
+    ((success++))
+else
+    log "$MCMD: converting large fasta file to fasta failed" 
+    ((failed++))
+fi
+ 
+((ntest++))
+if obiconvert -Z --fastq-output \
+              "${TEST_DIR}/gbpln1088.4Mb.fasta.gz" \
+                 > "${TMPDIR}/xxx.fastq.gz" && \
+   obiconvert -Z --fasta-output \
+              "${TMPDIR}/xxx.fastq.gz" \
+              > "${TMPDIR}/yyy.fasta.gz" && \
+   zdiff "${TEST_DIR}/gbpln1088.4Mb.fasta.gz" \
+                 "${TMPDIR}/yyy.fasta.gz" 
+then
+    log "$MCMD: converting large file between fasta and fastq OK" 
+    ((success++))
+else
+    log "$MCMD: converting large file between fasta and fastq failed" 
+    ((failed++))
+fi
+
 #########################################
 #
 # At the end of the tests
diff --git a/pkg/obiformats/embl_read.go b/pkg/obiformats/embl_read.go
index 4a5ca60..4150f57 100644
--- a/pkg/obiformats/embl_read.go
+++ b/pkg/obiformats/embl_read.go
@@ -187,13 +187,12 @@ func _ParseEmblFile(
 func ReadEMBL(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, error) {
 	opt := MakeOptions(options)
 
-	buff := make([]byte, 1024*1024*128) // 128 MB
-
 	entry_channel := ReadFileChunk(
 		opt.Source(),
 		reader,
-		buff,
+		1024*1024*128,
 		EndOfLastFlatFileEntry,
+		"\nID   ",
 	)
 
 	newIter := obiiter.MakeIBioSequence()
diff --git a/pkg/obiformats/fastaseq_read.go b/pkg/obiformats/fastaseq_read.go
index a3ab5c8..2a8114e 100644
--- a/pkg/obiformats/fastaseq_read.go
+++ b/pkg/obiformats/fastaseq_read.go
@@ -233,13 +233,12 @@ func ReadFasta(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, e
 
 	nworker := opt.ParallelWorkers()
 
-	buff := make([]byte, 1024*1024)
-
 	chkchan := ReadFileChunk(
 		opt.Source(),
 		reader,
-		buff,
+		1024*1024,
 		EndOfLastFastaEntry,
+		"\n>",
 	)
 
 	for i := 0; i < nworker; i++ {
diff --git a/pkg/obiformats/fastqseq_read.go b/pkg/obiformats/fastqseq_read.go
index 0000e73..cab6a5f 100644
--- a/pkg/obiformats/fastqseq_read.go
+++ b/pkg/obiformats/fastqseq_read.go
@@ -327,13 +327,12 @@ func ReadFastq(reader io.Reader, options ...WithOption) (obiiter.IBioSequence, e
 
 	nworker := opt.ParallelWorkers()
 
-	buff := make([]byte, 1024*1024)
-
 	chkchan := ReadFileChunk(
 		opt.Source(),
 		reader,
-		buff,
+		1024*1024,
 		EndOfLastFastqEntry,
+		"\n@",
 	)
 
 	for i := 0; i < nworker; i++ {
diff --git a/pkg/obiformats/file_chunk_read.go b/pkg/obiformats/file_chunk_read.go
index 17eb0c1..b42b883 100644
--- a/pkg/obiformats/file_chunk_read.go
+++ b/pkg/obiformats/file_chunk_read.go
@@ -4,8 +4,10 @@ import (
 	"bytes"
 	"io"
 	"slices"
+	"strings"
 
 	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiseq"
+	"git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obiutils"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -17,10 +19,102 @@ type FileChunk struct {
 	Order  int
 }
 
+type PieceOfChunk struct {
+	head *PieceOfChunk
+	next *PieceOfChunk
+	data []byte
+}
+
+func NewPieceOfChunk(size int) *PieceOfChunk {
+	data := make([]byte, size)
+	p := &PieceOfChunk{
+		next: nil,
+		data: data,
+	}
+	p.head = p
+	return p
+}
+
+func (piece *PieceOfChunk) NewPieceOfChunk(size int) *PieceOfChunk {
+	if piece == nil {
+		return NewPieceOfChunk(size)
+	}
+
+	if piece.next != nil {
+		log.Panic("Try to create a new piece of chunk when next already exist")
+	}
+
+	n := NewPieceOfChunk(size)
+	n.head = piece.head
+	piece.next = n
+
+	return n
+}
+
+func (piece *PieceOfChunk) Next() *PieceOfChunk {
+	return piece.next
+}
+
+func (piece *PieceOfChunk) Head() *PieceOfChunk {
+	if piece == nil {
+		return nil
+	}
+	return piece.head
+}
+
+func (piece *PieceOfChunk) Len() int {
+	if piece == nil {
+		return 0
+	}
+
+	if piece.next == nil {
+		return len(piece.data)
+	}
+	return len(piece.data) + piece.next.Len()
+}
+
+func (piece *PieceOfChunk) Pack() *PieceOfChunk {
+	if piece == nil {
+		return nil
+	}
+	size := piece.next.Len()
+	piece.data = slices.Grow(piece.data, size)
+
+	for p := piece.next; p != nil; {
+		piece.data = append(piece.data, p.data...)
+		p.data = nil
+		n := p.next
+		p.next = nil
+		p = n
+	}
+
+	piece.next = nil
+
+	return piece
+}
+
+func (piece *PieceOfChunk) IsLast() bool {
+	return piece.next == nil
+}
+
+func (piece *PieceOfChunk) FileChunk(source string, order int) FileChunk {
+	piece.Pack()
+	return FileChunk{
+		Source: source,
+		Raw:    bytes.NewBuffer(piece.data),
+		Order:  order,
+	}
+}
+
 type ChannelFileChunk chan FileChunk
 
 type LastSeqRecord func([]byte) int
 
+func ispossible(data []byte, probe string) bool {
+	s := obiutils.UnsafeString(data)
+	return strings.Index(s, probe) != -1
+}
+
 // _ReadFlatFileChunk reads a chunk of data from the given 'reader' and sends it to the
 // 'readers' channel as a _FileChunk struct. The function reads from the reader until
 // the end of the last entry is found, then sends the chunk to the channel. If the end
@@ -37,81 +131,86 @@ type LastSeqRecord func([]byte) int
 func ReadFileChunk(
 	source string,
 	reader io.Reader,
-	buff []byte,
-	splitter LastSeqRecord) ChannelFileChunk {
-	var err error
-	var fullbuff []byte
+	fileChunkSize int,
+	splitter LastSeqRecord,
+	probe string) ChannelFileChunk {
 
 	chunk_channel := make(ChannelFileChunk)
 
-	fileChunkSize := len(buff)
-
 	go func() {
+		var err error
 		size := 0
 		l := 0
 		i := 0
 
+		pieces := NewPieceOfChunk(fileChunkSize)
 		// Initialize the buffer to the size of a chunk of data
-		fullbuff = buff
 
 		// Read from the reader until the buffer is full or the end of the file is reached
-		l, err = io.ReadFull(reader, buff)
-		buff = buff[:l]
+		l, err = io.ReadFull(reader, pieces.data)
+		pieces.data = pieces.data[:l]
 
 		if err == io.ErrUnexpectedEOF {
 			err = nil
 		}
 
+		end := splitter(pieces.data)
+
 		// Read from the reader until the end of the last entry is found or the end of the file is reached
 		for err == nil {
 			// Create an extended buffer to read from if the end of the last entry is not found in the current buffer
-			end := 0
-			ic := 0
 
 			// Read from the reader in 1 MB increments until the end of the last entry is found
-			for end = splitter(buff); err == nil && end < 0; end = splitter(buff) {
-				ic++
-				buff = slices.Grow(buff, fileChunkSize)
-				l := len(buff)
-				extbuff := buff[l:(l + fileChunkSize - 1)]
-				size, err = io.ReadFull(reader, extbuff)
-				buff = buff[0:(l + size)]
-				// log.Warnf("Splitter not found, attempting %d to read in %d B increments : len(buff) = %d/%d", ic, fileChunkSize, len(extbuff), len(buff))
+			for err == nil && end < 0 {
+				pieces = pieces.NewPieceOfChunk(fileChunkSize)
+				size, err = io.ReadFull(reader, pieces.data)
+				pieces.data = pieces.data[:size]
 
+				if ispossible(pieces.data, probe) {
+					pieces = pieces.Head().Pack()
+					end = splitter(pieces.data)
+				} else {
+					end = -1
+				}
+				// log.Warnf("Splitter not found, attempting %d to read in %d B increments : len(buff) = %d/%d", ic, fileChunkSize, len(extbuff), len(buff))
 			}
 
-			fullbuff = buff
+			pieces = pieces.Head().Pack()
+			lbuff := pieces.Len()
 
-			if len(buff) > 0 {
+			if lbuff > 0 {
 				if end < 0 {
-					end = len(buff)
+					end = pieces.Len()
 				}
 
-				pnext := end
-				lremain := len(buff) - pnext
-				buff = buff[:end]
-				for len(buff) > 0 && (buff[len(buff)-1] == '\n' || buff[len(buff)-1] == '\r') {
-					buff = buff[:len(buff)-1]
-				}
+				lremain := lbuff - end
 
-				if len(buff) > 0 {
-					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++
-				}
+				var nextpieces *PieceOfChunk
 
 				if lremain > 0 {
-					buff = fullbuff[0:lremain]
-					lcp := copy(buff, fullbuff[pnext:])
+					nextpieces = NewPieceOfChunk(lremain)
+					lcp := copy(nextpieces.data, pieces.data[end:])
 					if lcp < lremain {
 						log.Fatalf("Error copying remaining data of chunk %d : %d < %d", i, lcp, lremain)
 					}
 				} else {
-					buff = buff[:0]
+					nextpieces = nil
 				}
 
+				pieces.data = pieces.data[:end]
+
+				for len(pieces.data) > 0 && (pieces.data[len(pieces.data)-1] == '\n' || pieces.data[len(pieces.data)-1] == '\r') {
+					pieces.data = pieces.data[:len(pieces.data)-1]
+				}
+
+				if len(pieces.data) > 0 {
+					// log.Warnf("chuck %d :Read %d bytes from file %s", i, io.Len(), source)
+					chunk_channel <- pieces.FileChunk(source, i)
+					i++
+				}
+
+				pieces = nextpieces
+				end = -1
 			}
 		}
 
@@ -119,10 +218,11 @@ func ReadFileChunk(
 			log.Fatalf("Error reading data from file : %s", err)
 		}
 
+		pieces.Head().Pack()
+
 		// Send the last chunk to the channel
-		if len(buff) > 0 {
-			io := bytes.NewBuffer(slices.Clone(buff))
-			chunk_channel <- FileChunk{source, io, i}
+		if pieces.Len() > 0 {
+			chunk_channel <- pieces.FileChunk(source, i)
 		}
 
 		// Close the readers channel when the end of the file is reached
diff --git a/pkg/obiformats/genbank_read.go b/pkg/obiformats/genbank_read.go
index 34fed24..4d57235 100644
--- a/pkg/obiformats/genbank_read.go
+++ b/pkg/obiformats/genbank_read.go
@@ -223,13 +223,12 @@ func ReadGenbank(reader io.Reader, options ...WithOption) (obiiter.IBioSequence,
 	opt := MakeOptions(options)
 	// entry_channel := make(chan _FileChunk)
 
-	buff := make([]byte, 1024*1024*128) // 128 MB
-
 	entry_channel := ReadFileChunk(
 		opt.Source(),
 		reader,
-		buff,
+		1024*1024*128,
 		EndOfLastFlatFileEntry,
+		"\nLOCUS       ",
 	)
 
 	newIter := obiiter.MakeIBioSequence()
diff --git a/pkg/obioptions/version.go b/pkg/obioptions/version.go
index d23f1c8..bde6c12 100644
--- a/pkg/obioptions/version.go
+++ b/pkg/obioptions/version.go
@@ -8,7 +8,7 @@ import (
 // corresponds to the last commit, and not the one when the file will be
 // commited
 
-var _Commit = "f21f51a"
+var _Commit = "937a483"
 var _Version = "Release 4.4.0"
 
 // Version returns the version of the obitools package.